JPS60190941A - Dental diagnostic apparatus - Google Patents

Abstract

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

Description

Detailed Description of the Invention (Technical Clarification of the Invention) The present invention provides a method for fixing a dental implant to the jawbone when installing an artificial prosthesis 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, since there is no tooth root to support the crown, treatment is performed using methods such as a bridge.

However, these treatments place an excessive load on the supporting natural teeth, eventually leading to a situation where they must be extracted as well.

Therefore, research is being conducted on a treatment method in which an implant, also known as an artificial tooth root, is implanted and identified in the jawbone, and an artificial crown is placed 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 implant is susceptible to small infections from the interface, and once infection occurs, the implant must be removed.

In contrast to macroscopic mechanical bonding methods such as screw-shaped implants, implants are made using microporous materials such as sintered alumina, and bone naturally grows into the pores, resulting in implants that have a microscopic mechanical bond. Types of implants that attach to bone through a set of mechanical connections are also being 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 conducted on implants in which a metal core is coated with bioactive glass (see Japanese Patent Laid-Open No. 118746/1983).

Research is also underway into a treatment method that uses artificially synthesized hydroxyapatite, the main component of hydroxyapatite, 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,
There are individual differences among patients, and 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 can no longer be expected. As a result, complete fixation of the implant is no longer achieved.

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

However, it seemed difficult to nondestructively diagnose whether implant fixation was successful or unsuccessful. This is because you should not destroy the fixation that has been completed by diagnosing it by rough means, and you cannot confirm whether it is completely fixed by touching it with your hands. Furthermore, with the commonly used X-ray photographs, diagnosis is not possible except in cases of poor fixation where the defective granulation is extremely thick and developed.

(Object of the Invention) Therefore, it is an object of the present invention to provide an implant that is implanted in the jawbone and is fixed (herein, the term "fixation" 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 the tooth is fixed by mechanical coupling).

(Summary of the invention) Ultrasonic diagnostic method is a non-destructive measurement method.
Conventional ultrasound diagnostic methods utilize the fact that the propagation speed of ultrasound waves differs depending on the substance, and attempts were made to detect defective granulation using this ultrasound diagnostic method, but ultrasound diagnosis through bone does not allow for the attenuation of ultrasound waves. was so large that diagnosis was impossible.

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, and (c) is a model. is the jawbone). That is, when defective granulation occurred, the spring (B) was considered to be quite soft, and when it was completely fixed, the spring (B) 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 (a), when the applied frequency matches the natural frequency of the vibration system consisting of the implant (a) and the spring (b), the vibration system will resonate. The implant (a) should make a large-amplitude vibration sound, and if we use the resonance phenomenon, even if we apply a small-amplitude vibration to a living body that does not have a color tube, the amplitude of the resonance frequency will become large, making it easy to detect. Will. Theoretically, the harder the spring (b) is, the higher the resonance frequency will be, so we thought that the fixation condition could be diagnosed from the resonance frequency.

Therefore, the inventors decided to prototype a test device and conduct animal experiments.In order to observe the resonance phenomenon, the frequency of the ultrasonic vibrations applied to the implant was varied over time.
Since detecting the resonant frequency takes too much time, we decided to apply ultrasonic vibrations containing a wide range of frequency components from low to high frequencies to the Innoplant. 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 current and the amplitude will become large, while the other components have relatively small vibrations, so they will not resonate. This is because only the frequency 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 an ultrasonic vibration sound containing a wide range of frequency components from low frequencies to high frequencies; An ultrasonic vibration transmitting means (2) for transmitting ultrasonic vibrations from the implant to the implant, and an ultrasonic vibration frequency measuring means (3) for measuring the resonance frequency by contacting the implant,
Invented a dental diagnostic device that diagnoses the identification status of implants based on resonance frequency, and filed a patent application (patent application filed in 1973).
8-232534).

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 inventors developed the present invention by improving the previous invention to make diagnosis easier.

In other words, it has been empirically known that the resonant frequency (fo) at the time of success is different from the resonant frequency (fx) at the time of failure, and generally when a resonance phenomenon occurs, the amplitude becomes considerably large, so whether there is resonance or not. They found that it is easy to investigate, and therefore, by detecting the presence or absence of a resonance phenomenon at the resonance frequency (fo or fX), it is possible to easily diagnose success or failure.
The present invention has been accomplished.

Therefore, the present invention provides an ultrasonic vibration source (1) that generates ultrasonic vibration containing at least a predetermined resonance frequency (f) component;
Ultrasonic transmission means (2) for transmitting ultrasonic vibrations from the vibration source to the implant; and detection means (3) for contacting the implant and detecting the presence or absence of a resonance phenomenon at the predetermined resonance frequency (f). Provided is a dental diagnostic device that diagnoses the fixation status of an implant based on the presence or absence of a resonance phenomenon at a predetermined frequency (f).

In the present invention, the predetermined resonant frequency (f) means the resonant frequency (fo) when the implant is successfully fixed or the resonant frequency (fx) when the implant is unsuccessfully fixed. It is necessary to diagnose whether it is a success or not, and in the latter case whether it is a fixed failure or not.

Since such predetermined resonance frequencies (fo and fx) change depending on the mass and shape of the implant, the above-described predetermined resonance frequencies (fo and fx) vary depending on the mass and shape of the implant.
Using the diagnostic device of 534), the resonant frequency (
fo) and the resonance frequency (fx) at the time of fixation failure.

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 excavator (1b) includes a piezoelectric element and an ultrasonic vibration oscillator (1b). It consists of a pair of electrodes sandwiching the. The electric signal is sent to the oscillator (1b
), ultrasonic vibrations consisting of various frequency (vibration frequency) components are generated depending on the waveform and input time.

If you try to generate ultrasonic vibrations consisting of purely a single frequency (fo or fx), the same frequency (fo or fx)
It is necessary to obtain the sine wave electric signal x) from the generating means (1a) and input it to the oscillator (1b) for an infinite time.

However, in reality, there are biological and temporal differences among patients, and fo and fX are distributed within a certain range, so fo and fx cannot be specified as a single value for a new patient, and in the end, Often it is only possible to estimate that fo and fX are within a certain range.

Therefore, the ultrasonic vibration input to the implant is fO±
It is practical to use one that includes frequency components in the band Δf or fX±Δf'. In this case, f
generating means (
1a) for a period of Δt and input to the oscillator (1b). The width of the band can be changed by adjusting the time Δt. That is, a large deviation in Δt will narrow the band, and conversely, a small deviation in Δt will widen the band.

For example, here 100 KHz to 150 KHz (Δt=50
If you want to obtain ultrasonic vibration in the frequency band of 12 KHz),
Determine the time Δt for applying a 5 KHz sine wave electrical signal. However, Δt is the half width.

According to the Fourier transform formula, when g(t)=0, when g(t)=cosωot, then g(t)=0, so it is only necessary to integrate. Here, if ω=2πf and ω0=2πfo, then when f=fo, G(f)=Δt/2, so the half value is Δt/4.

Therefore, from equation (1), equation (2) is a transcendental equation, so if it is solved by numerical calculation, from equation (3), the half-width Δf is Δf = 50 KHz. If it is desired to obtain ultrasonic vibration with a half width, it is sufficient to input a 125 KHz sinusoidal electric signal for 24.2 μsec to the oscillator (1b).

In some cases, ultrasonic vibrations having frequency components fo±Δf and fx±Δf′ may be generated simultaneously or preferably at intervals of time and input to the implant; The sine wave electric signal of f0 and that of fx may be obtained from the generating means (1a) at predetermined times, simultaneously or preferably at intervals of time, and inputted to the oscillator (1b). .

Further, ultrasonic vibrations consisting of broadband frequency components may be used. To obtain this vibration, the generating means (1a) generates a pulsed electric signal having a rectangular wave or a waveform close to it, and only one pulse is generated. 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 (lb) are also extremely short-term, 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. However, there is no problem if the detection means (3) can detect the resonance phenomenon, but such a detection means (3) requires more expensive equipment, and it is difficult to realize the detection means (3) at low cost and to improve its reliability. In order to increase this, it is preferable to cause the resonance phenomenon to occur repeatedly.

For this purpose, the electric signal generated by the generating means (1a) is
The signal 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, compared to continuously inputting ultrasonic vibration sounds to the implant over a long period of time. because,
If input continuously for a long time, (a) Perturbation transmission means (2)
There is a risk that heat will be generated between the implant and the implant, which may have an undesirable effect on the living body, and (b) the amplitude of the resonant vibration will gradually increase, and the fixed state may eventually 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 typically made of metal. The shape does not matter, but
Because the implant is small, it is naturally limited. Particularly in the case of a buried implant, the implant is covered with the gingiva and cannot be brought into direct contact with the implant, so a needle shape that can penetrate the gingiva is preferable.

On the other hand, in the case of an implant whose visible part protrudes from the gums, it can be directly touched, so there is no need to force it into a needle shape, and it may be hemispherical.

On the other hand, the detection means (3) for detecting the presence or absence of a resonance phenomenon at a predetermined resonance frequency (fo or fx) is generally an ultrasonic deep probe (3a) that receives resonance vibration and converts it into a high-frequency electric signal. ), an amplifier (3b) that amplifies the converted high-frequency electrical signal as necessary, and a punt-pass filter (corresponding to fo or fX) that passes only a narrow band (corresponding to fo or fX) containing a predetermined frequency component from the amplified high frequency. 3c), a rectifier circuit (3d) that converts the high frequency electrical signal that has passed through it into a DC signal, compares the intensity level of the DC electrical signal with a predetermined comparison level, and if it is higher than the comparison level, the electrical signal It consists of a comparator (3e) that outputs , and a display means (3f) that displays ON-OFF based on the output of the U comparator. In this example, when the display means displays ON, it indicates that a resonance phenomenon has occurred at a predetermined frequency (fo or fx), and when the display means does not display ON (that is, O
(FF) indicates that there was no resonance phenomenon. (3
b) The subsequent processing of electrical signals 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 fo or fx leaves a feeling of anxiety in the diagnosis, so as mentioned earlier, one diagnostic device can detect vibrations at both frequencies using a switching means. A device that oscillates sequentially and can detect the presence or absence of a resonance phenomenon is preferable. Furthermore, using an ultrasonic vibration source (1) containing both f0 and fx components, an amplifier (
A band pass filter (3Co) that divides the output from 3b) into two and passes one through fo → rectifier circuit (3do) →
The comparator (3eo) → display means (3fo), and the other is a bandpass filter (3C) that passes fX.
x) → Rectifier circuit (3dx) → Comparator (3ex)
→ display means (3fx), thereby fo and f
The presence or absence of a resonance phenomenon at 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 fo) or failed (with fx), so the display means (3fo) and (3f
x) and simply "success", "failure", "undecided"
It is also possible to use a display means that lights up any one of the following. Further, instead of displaying "success", "failure", and "undetermined", a green, red, or yellow lamp may be lit.

In the previous explanation, a narrow band bad pass filter (
3c), the frequency of the ultrasonic filament applied to the implant was originally f0±Δf straddle fx±Δ
If the frequency is limited to the narrow band f', fo or fX, only resonance phenomena can occur at those frequencies, so there is no need to use the bandpass filter (3e) on the receiving side.

As is already well known, the ultrasonic probe (3a) contacts an implant to receive ultrasonic vibrations and transmits the ultrasonic vibrations to a piezoelectric element (3a1) and a pair of electrodes. It consists of a sandwiched 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 nail-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 m, a length of 9.0 mm, and a weight of 0.8 g.
The iron-based cobalt-nickel alloy core (d) has a thickness of 0.
It is coated with 5mm bioactive glass (e).

This implant has a ``indentation'' (f) 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 situation immediately after implantation, where (G) indicates the gingiva and (C) indicates the jawbone.

As a result of repeated animal experiments, this implant has been empirically shown to have a
Resonant vibrations of 0 to 150 KHz are observed, and if failure occurs, resonant vibrations of 20 to 50 KHz are observed, and if neither is determined yet, 50 KHz and 10 KHz are observed.
A resonant vibration between 0KHz and 0KHz is observed, and in this case,
Eventually success (100~150KHz) or failure (20~
50KHz).

Therefore, when this implant is implanted in a laboratory animal, fo = 100 to 150 KHz or fX = 20 to 50 KHz.
It should be KHz.

FIG. 4 is a block diagram showing the overall structure of the diagnostic apparatus of this embodiment, and (1a) is a pulsed electric signal generating means. As a result, the time period of 7 to 42 μsec as shown in FIG. pulse width (Tp), amplitude (Ap) of 1 to 30 volts and 0.6 msec. A pulsed electrical signal having a pulse interval (Rp) of is repeatedly generated. This electrical signal is the sixth
It has a frequency spectrum as shown in the figure, 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 vibration is 0.6msec. occurs repeatedly every time.

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) here uses a stainless steel needle with a diameter of about 1 mm and a length of about 30 mm.

On the other hand, as shown in FIG. 4, the resonance vibration of the implant is received by an ultrasonic probe (3a) k brought into contact with the implant, and is converted into a high frequency electric signal. This electrical signal is very weak, so it is led to an amplifier (3b) and
Amplify by 00 times. The amplified high-frequency electrical signal is then passed through a band-pass filter (3e) that passes only frequency components of 100 to 150 KHz, and its output is led to a rectifier circuit (3d) where it is converted into a DC signal.

The converted DC signal is led to the converter (3e),
Here, 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, and guides the output of (3e) to display means (3f). This display means (3f)
is "successful" or "successful" only when it receives the output of (3e).
The "power saving" indicator lamp lights up.

When using the above device and the indicator lamp lights up, we cut the gums to expose the implant and added it manually, and the implant was firmly fixed.
Even if I pulled it using a dental bench, it did not come out. 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 could be easily pulled out by hand and bad granulation had occurred, or the implant could not be pulled out by hand but could be pulled out by pulling it on a dental bench. Ta.

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 has been found that even if the diagnosis is made before complete fixation, there is no obvious adverse effect on bone formation (that is, complete fixation).

In the above explanation, the "probe (3a)" is a separate example from the "oscillator (1b) and vibration transmission means (2)," but the electrical signal processing may be performed as appropriate. If you can do it,
It is also possible to have a single painter and (a) have them function alternately in chronological order, or (b) have them function simultaneously.

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 identification status of an implant with respect to the jawbone.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram showing, as a model, how the implant (A) is implanted in the jawbone (C). 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. FIG. 4 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 electrical 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. [Explanation of symbols of main parts] l...Ultrasonic vibration generation source 2...Ultrasonic vibration transmission means 3...Resonant vibration sensing means 3a...Ultrasonic probe 3b...Amplifier 3c...Bant pass filter 3d... Rectifier circuit 3e... Comparator 3f... Display means a... Implant ro... Spring, ji... Jaw bone d... Core body e... bioactive glass... depression... gingiva.

Claims (1)

[Scope of Claims] 1. Ultrasonic vibrating mud (1) that generates ultrasonic perturbation containing at least a predetermined resonance frequency (f) component, ultrasonic transmission means for transmitting ultrasonic vibration from the vibration source to the implant. (2), 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 for diagnosing the fixation status of an implant based on the presence or absence of a resonance phenomenon at a predetermined frequency (f). 2. 2. The dental diagnostic apparatus according to claim 1, wherein the predetermined resonance frequency (f) is a resonance frequency (fo) at the time of successful implant fixation. 3. The dental diagnostic apparatus according to claim 1, wherein the predetermined resonance frequency (f) is a resonance frequency (fx) when the implant fixation fails.