JP2000005201A - Device for detecting periapex's position - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect precisely a periapex even if there is some leakage from a root. SOLUTION: In case a response value which corresponds to the impedance between a pole 2 for measuring the length of a root and a pole 3 for a mouth are influenced by leakage of bloods or liquid medicine from a root 1a, a compensating means 9 that compensates the abnormal quantity of the response value caused by the leakage and removes its influences and a compensation selecting means 7 and 9a to shift a mode to that of the compensating means 9 are provided. Thus, even in case leakage of liquids occurs, it makes possible to continue operation without stopping measurement or cleaning inside and outside of the teeth.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an apical position detecting device used for dental diagnosis and treatment.

[0002]

2. Description of the Related Art As an apical position detecting device, an impedance between a root canal and a soft tissue in an oral cavity is regarded as an equivalent circuit in which resistance and capacitance are combined in series and in parallel. Is generally configured to calculate the position of the tip of the measurement electrode based on the change state of the response value corresponding to the following. That is, these devices
The equivalent circuit is applied when a measurement voltage is applied between the measurement electrode inserted into the root canal and the oral electrode in contact with the soft tissue in the oral cavity, and a measurement current flows between the two electrodes. Becomes very small and the capacitance becomes large,
For example, the arrival at the apex is detected by utilizing the fact that the phase and waveform of the measured current change significantly, and the result is displayed. In addition, since the root canal length can be measured if the position of the apex can be specified, this type of device is sometimes called a root canal length measuring device.

[0003] As a specific detection method, a shift in the phase of the current or a shift in the waveform with respect to the waveform of the measured voltage is detected, and the shift that increases when the measurement electrode approaches the apical tip is used (for example, a special method). See JP-A-4-73056),
Calculates the ratio of each response value obtained when two types of measurement voltages having different frequencies are applied, and utilizes the fact that the ratio increases as the measurement electrode approaches the apex (for example, Japanese Patent Application Laid-Open No. 4-64354). Japanese Patent Application Laid-Open No. HEI 2 (1999) -1995 discloses a method of calculating the difference between the above response values and utilizing the fact that the difference decreases as the measurement electrode approaches the apex.
-297359).

[0004] Here, the response value is a measured current value itself or a numerical value obtained by performing a process such as converting the current value into a phase shift as described above, and corresponds to the impedance to be measured. With the value
In this specification, the word "response value" is used in this sense.

In each of the above-described devices, the measured current has a relatively small response value when the measuring electrode is located near the intermediate position of the root canal for a fundamental reason of the measurement, and increases rapidly as approaching the apex. This shows the change. In the first stage of inserting the measurement electrode into the root canal, the electrode is exposed to the inner wall of the root canal wetted with a liquid of strong electrolyte such as blood or chemicals (hereinafter referred to as chemicals) or the chemicals accumulated in the root canal. When touched,
In many cases, the current value rises once due to the influence of the capacity component of the chemical solution, and the effect becomes smaller and the value decreases as the electrode is inserted to the middle position of the root canal in many cases. For this reason, if the value in this range is used as it is for display, the judgment will be incorrect or measurement will be impossible, so care must be taken in handling and displaying data until the measured current starts to increase again, but this problem has already been proposed. Have been solved by various measures taken, for example, in Japanese Patent Application Laid-Open No.
The display mode in this range is different from the display mode after the measurement current starts to increase again.

[0006] The above-mentioned publications are designed to prevent the measurement result from being greatly affected by the condition inside the root canal, that is, whether the inside of the root canal is in a dry state or in a wet state with chemicals. Therefore, various detection methods as described above are employed, and a certain effect is obtained. However, these prior arts all focus on only the state inside the root canal, and do not consider the case where the drug solution leaks out of the tooth from the root canal.

[0007] That is, if there is such a leakage of chemicals (hereinafter, referred to as liquid leakage), the capacitance is further inserted in parallel with the above-described equivalent circuit, and the impedance of the equivalent circuit is determined by the measurement electrode. Since the value is about the same as or higher than that when the apex is reached, the same display as when the apex is reached is performed immediately after the measurement electrode is inserted into the root canal, and the measurement cannot be continued. Therefore, in such a case, it is necessary for the operator to judge that there is a liquid leak and to stop the measurement without erroneously assuming that the display is the apical reach display, and to stop the measurement around the tooth before restarting the measurement. The root canal must be thoroughly washed. For this reason, a cumbersome cleaning operation is forced on the operator, and the efficiency of medical treatment is reduced.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to pay attention to these points and to make it possible to accurately detect the apical arrival even when there is a leak from the root canal. .

[0009]

In order to achieve the above object, the apex position detecting device of the present application uses a tip of the measuring electrode based on a change in a response value corresponding to the impedance between the measuring electrode and the oral electrode. In the apical position detection device configured to detect the position, when the response value is affected by leakage of blood or a drug solution from a root canal, the response value due to the leak of these drug solutions is detected. Compensation means for compensating for the abnormal portion and removing its influence, and compensation selection means for switching to a compensation mode by this compensation means are provided.

As the above-mentioned compensation selecting means, for example, those configured to detect an abnormal response value and automatically switch to the compensation mode, those configured to switch to the compensation mode by manual operation, and the like are employed. it can. With such a configuration, it is not necessary to stop the measurement or clean the inside and outside of the tooth even if there is liquid leakage, and the measurement operation can be continued as it is.

The compensating means detects that the response value or the converted value obtained by performing a certain process on the response value has reached the maximum value or the minimum value, and based on the maximum value or the minimum value, determines the reference value. When the response value obtained subsequently or the converted value obtained by performing a certain process on the response value changes by a predetermined judgment value with respect to the reference value, the tip of the measurement electrode is apical or It is configured to determine that it has reached the vicinity. As described above, since the converted value is a value obtained by performing a certain process on the response value, it is a value corresponding to the impedance measured in the same manner as the response value. The resulting abnormal response value is removed, and the measurement can be performed without being affected by liquid leakage.

The above-mentioned response value is obtained, for example, by applying an AC measurement voltage between the measurement electrode and the oral electrode, comparing the waveform of the measurement voltage with the waveform of the measurement current flowing between the electrodes, and comparing the voltage waveform with the current. It is obtained by using the phase shift of the waveform as a response value.

The above-mentioned response value is obtained by applying a measurement voltage as a set of at least two single-shot waveforms having different transient phenomena caused by impedance including a capacitance component between the measurement electrode and the oral electrode. It can also be obtained by using the deviation of the waveform of a set of flowing measurement currents as the response value.

When a response value is obtained by the above-described method, the minimum value is used as a reference value so that an abnormality in the response value due to liquid leakage can be prevented as described in detail in the following embodiments of the invention. Removed.

Further, at least two types of measurement voltages having different frequencies are applied between the measurement electrode and the oral electrode, and a ratio of response values at each frequency obtained between the two electrodes is obtained. The value obtained by dividing the value by the value is used as the reference value, and the value obtained by dividing the ratio of the response value obtained subsequently by the maximum value or the minimum value is used as the converted value, thereby obtaining the response value resulting from the liquid leakage. Abnormalities can be eliminated.

Further, it is possible to provide a setting means for arbitrarily setting a judgment value used for judging that the tip of the measuring electrode has reached the apex. With such a configuration, it is possible to more appropriately remove the abnormal portion of the response value due to the liquid leakage.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described in which a measurement voltage is formed into a repetitive waveform to detect a phase shift of a measurement current. FIG. 1 is a block diagram, FIG. 2 is an explanatory diagram of a waveform, and FIGS. 3 to 6 are explanatory diagrams of determination of a reference value and determination of arrival at an apex. In FIG. 1, 1 is a tooth, and 1a and 1b are roots thereof. Canal and apical, 2
Is a measuring electrode, 2a is its tip, 3 is an oral electrode, 4 is a measuring signal generating circuit that outputs an AC signal continuously or at predetermined intervals, 5 is a current detecting resistor, 6 is a comparing circuit, and 7 is a control unit. , 8 are a display unit, 9 is a compensation circuit, and 9a is compensation selection means for switching to a compensation mode. The control unit 7 controls the operation of the entire circuit, and is configured using, for example, a CPU.

The measurement signal generation circuit 4 generates a repetition signal of, for example, 1 kHz as a measurement voltage, and applies the signal to the measurement electrode 2 such as a reamer or a file via the resistor 5. The measurement current flowing between the measurement electrode 2 and the oral electrode 3 is detected in the form of a voltage of the measurement electrode 2, and this detection voltage corresponds to the one corresponding to the impedance of the equivalent circuit between the measurement electrode 2 and the oral electrode 3. The detection voltage and the measurement voltage are input to the comparison circuit 6.

In FIG. 2, A is a measurement voltage waveform output from the measurement signal generation circuit 4, B is a detected measurement current waveform, and B ₁ and B ₂ are the tip 2a of the measurement electrode 2 at the cervical region, respectively. And the waveforms when it is located near the apex.
The C is the output waveform of the comparator circuit 6, a waveform when C ₁ and C ₂ is the front end 2a of the measuring electrode 2 is located near the apex cervical and roots, respectively. A, B, and C in FIG. 1 show locations where these signal waveforms can be obtained.

Since the equivalent circuit between the measurement electrode 2 and the oral electrode 3 is regarded as a circuit in which resistance and capacitance are combined in series or in parallel, when the measurement voltage A is, for example, a sine wave, the waveform B of the measurement current ₁ and B ₂ be the same sine wave and the phase will be different depending on the magnitude of the capacitance. Therefore, when the capacitance component of the equivalent circuit tip 2a of the electrode 2 is closer to the vicinity of the root apex is increased, the phase shift of the waveform B with respect to the waveform A increases, the output waveform C ₂ in accordance with the phase difference width of the pulse is larger than C _1. That is, the comparison circuit 6 is configured to output a pulse voltage having a width corresponding to the phase difference between the two voltages as a response value, and the control unit 7 detects a change state of the response value and determines a reference value. At the same time, the apical arrival is determined based on a subsequent change, and the result is displayed on the display unit 8. The determination of the reference value and the determination of the apical arrival are performed as follows.

FIG. 3 illustrates the relationship between the position of the tip 2a of the measurement electrode 2 and the pulse width of the pulse voltage output from the comparison circuit 6, that is, the response value. The horizontal axis in the figure is the distance (unit: m) from the tip 2a to the apex 1b expressed as a negative number.
m), and the vertical axis is the response value (unit: mA) expressed by replacing the pulse width with the current. This response value quantitatively expresses the phase difference corresponding to the impedance of the equivalent circuit. The absolute value of a number is not that significant. FIG.
Indicates a case where physiological saline is accumulated in the root canal, and a solid line illustrates a state where the physiological saline is not leaking, and a broken line illustrates a state where the physiological saline is leaking.

First, the case where the physiological saline indicated by the solid line is not leaked will be described. When the electrode 2 comes into contact with the physiological saline inside at the first stage when the measuring electrode 2 is inserted into the root canal 1a,
The value rises once as shown in the figure due to the effect of the capacitance component,
As the electrode 2 is inserted into the root canal 1a, its effect becomes smaller and the numerical value decreases. Further, when the electrode 2 advances to the vicinity of the intermediate position of the root canal 1a, the numerical value stops decreasing, and as the electrode 2 approaches the apex 1b, the numerical value starts to increase conversely, and increases considerably near the apex 1b. In the range until the numerical value starts to increase, it is erroneous to use this numerical value as it is for display, but this problem can be solved by a known method as described above. Only the range from the intermediate position of the root canal related to the present invention to a position slightly beyond the apex will be described.

On the other hand, the tendency of the change is the same in the case of the broken line, but the extra capacitance is inserted into the equivalent circuit due to the physiological saline leaking out of the tooth. It will be larger than the case. Therefore, the difference between the upper and lower sides corresponds to an abnormal part of the response value due to the liquid leakage.

It has been clinically confirmed that the value when the measuring electrode reaches the vicinity of the apex is substantially constant when there is no liquid leakage. Therefore, in a conventional apparatus, it is generally determined that the apex reaches the apex. The judgment value is set to a certain value in advance. Assuming that this was 36, for example, in the case of FIG.
As shown by the circles, the solid line is 0.5
mm, exactly coincident with the apical stenosis, but about 2 mm
It will be in the foreground and will be a completely inappropriate decision. Also,
If the judgment value is set higher than this, there is a possibility that the arrival judgment will be made at the position past the apex with the solid line, and if it is set lower, the arrival judgment may be made at all positions with the broken line There is also. Therefore, unless the abnormal part of the response value caused by the liquid leakage is compensated for and its influence is not removed, reliable measurement becomes impossible at all.

Here, paying attention to the minimum value of the broken line, 35 is the minimum value, and FIG. 4 is a plot of a value obtained by subtracting the minimum value from each value in FIG. As can be seen from FIG. 4, the value corresponding to the pulse voltage output from the comparison circuit 6 is not used as a response value as it is,
The conversion value obtained by performing the process of reducing the minimum value is used. For example, as shown by a circle, the conversion value of 5.
The apical stenosis can be detected by setting the vicinity of 5 as the judgment value of the arrival judgment, and the apex can be detected by setting the vicinity of 8 as the judgment value of the arrival judgment.

FIGS. 5 and 6 show data processing similar to FIGS. 3 and 4 for the case where a mixed solution of physiological saline and a chemical solution (sodium hypochlorite) is accumulated in the root canal. Are shown by a solid line when the mixture is not leaking, and by broken lines when the mixture is leaking. Also in this example, the dashed line in FIG. 5 is much higher than the solid line in the same manner as in the case of only the physiological saline solution, and proper measurement cannot be performed when there is a liquid leak. On the other hand, in FIG. 6 in which a value obtained by subtracting 36.5 of the minimum value of the broken line from each numerical value in FIG. If the vicinity of 9 is set as the judgment value of the arrival judgment, the apex can be detected respectively.

The present invention takes advantage of this feature. In the above case, a numerical value corresponding to the detected impedance, that is, the minimum value of the response value is used as a reference value, and the minimum value is subtracted from each response value. Is a converted value, for example, by performing the correction that the numerical value shown above is a determination value,
This eliminates the effects of leakage from the root canal, such as chemicals, so that measurement can be performed without any problem even if there is leakage. Such data processing is performed by the control unit 7 and the compensation circuit 9.

That is, the control section 7 has a function of a compensation selecting means, and the response value shows a large value immediately after the measurement electrode 2 is inserted into the root canal 1a. If the value is larger than the preset value, the control unit 7 determines that there is a liquid leak and switches to the compensation mode. In this mode, the control unit 7
, A change in the response value is constantly monitored, and a numerical value immediately before the response value starts to increase, for example, a numerical value 35 at a position 3 mm before the broken line in FIG. 3 is set as a reference value. As a result, the operation is switched to that shown in FIG.
Is monitored by monitoring the change.
When it reaches 5, it is determined that the apex stenosis has been reached.

As described above, the switching to the compensation mode is not automatically performed, and a manually operated selection switch 9a such as a push button switch is provided as compensation selection means as shown by a broken line in FIG. When the response value shows a value that is much larger than usual immediately after the insertion of 2 into the root canal 1a, the operator may operate the selection switch 9a to switch to the compensation mode. Therefore, in the case of automatic switching, a selection device is unnecessary and a device with good operability can be obtained, and a device provided with a selection switch has a simpler control circuit, which is advantageous in cost.

In the above description, specific numerical values are exemplified as the judgment values. However, the judgment values may be slightly different depending on the use conditions, the type of the chemical solution, and the like. Value is set in advance. Further, instead of fixing the determination value in this way, a determination value setting operation unit 9b may be provided as shown by a broken line in FIG. 1 so that manual setting can be appropriately performed according to use conditions, types of chemicals, and the like. By changing the determination value accordingly, it is possible to more appropriately remove the abnormality of the response value.

According to the above procedure, the converted value of FIG. 4 or FIG. 6 when there is liquid leakage, and the response value of the solid line of FIG. 3 or FIG. Displayed in real time. In FIGS. 4 and 6, conversion values are shown over the entire range of the horizontal axis. However, since the conversion values are actually used only after switching to the compensation mode, display is performed only thereafter. The display itself may be the same as that of the conventional device. For example, in addition to the digital display and the pointer display, various displays such as a single display by voice or other means are used alone, or a combination thereof is used. be able to. Further, since the specific display does not need to be the response value or the converted value described above, for example, the distance to the apex 1b is displayed by back-calculating the numerical value on the horizontal axis of each figure from the response value or the converted value. What is necessary is just to display in the most desirable mode.

The above is an example in which the phase shift between the voltage waveform and the current waveform is used as the detected value. The measured voltage having a single-shot waveform is used, and the shift between the measured voltage and the measured current waveform caused by the transient phenomenon is used as the response value. It can also be used. FIG. 7 is a block diagram of the device in this case, and FIG. 8 is an explanatory diagram of waveforms.
7, reference numeral 11 denotes a measurement signal generating circuit that outputs a single-shot waveform signal, 12 denotes a timing controller, 13 denotes a memory, 14 denotes a waveform comparison circuit, and 15 denotes an AD converter. is there.

The measurement signal generation circuit 11 is configured to generate a triangular wave having an accurate slope and amplitude as a measurement voltage, for example, as shown in a waveform D in FIG. Applied. The AD converter 15 converts the voltage generated at the measuring electrode 2 corresponding to the measuring current, that is, the current waveform E, into AD at a predetermined unit time under the control of the timing controller 12, and converts each time T _{1 to} T ₆
Is recorded. Further, the memory 13 stores the peak value of the time T ₁ through T ₆ of the resultant current waveform when the tip 2a of the electrode 2 reaches the root apex 1b as the reference data, the waveform comparator circuit 14 memory 13 is compared with the load current waveform E obtained by the AD converter 15, and a signal voltage corresponding to the comparison result is output.

That is, when the tip 2a of the electrode 2 is located at, for example, the cervical region, the current waveform E ₁ has a triangular waveform equivalent to the measured voltage waveform D because there is almost no equivalent impedance capacitive component. Is large and the output of the waveform comparison circuit 14 is small. However, when the tip 2a of the electrode 2 is capacitive component of the equivalent impedance is increased approaching the vicinity of the root apex, the load current waveform E ₂ under the influence of transients is deviation between the waveform of the reference data becomes smaller, the waveform comparison circuit 14 The output increases.

In the above example, the output of the waveform comparison circuit 14 is used as a response value, whereby the position of the tip 2a of the electrode 2 can be detected. Although the graph of the specific response value is omitted, the response value in the case where there is no liquid leakage and the response value in the case where there is a liquid leak are almost the same as those in FIGS. In this example as well, if there is a liquid leak, the apical stenosis or the apex can be appropriately detected by switching to the compensation mode.

Next, an example will be described in which at least two types of measurement voltages having different frequencies are applied between the measurement electrode and the oral electrode, and the ratio of the response values at each frequency obtained between both electrodes is used. . In the block diagram shown in FIG. 9, reference numerals 21 and 22 denote measurement signal generation circuits that output an AC signal, 21 denotes an oscillator that outputs a measurement voltage of a frequency f, and 22 denotes an oscillator that outputs a measurement voltage of a frequency 5f. I have. 23 is an analog multiplexer, 24 is a buffer, 25 is a timing controller, 26 is a waveform shaping circuit, 27 is an AD converter, 28 is a control unit, 29 is a display unit, and 30 is a compensation circuit.

The timing controller 25 controls the operation timing of each circuit. Under this control, the analog multiplexer 23 switches the oscillators 21 and 22 at a predetermined cycle, and the output is measured via the buffer 24. Applied to the electrode 2. The measured current is detected in the form of a voltage by the resistor 5, shaped by a waveform shaping circuit 26, and then converted into digital data by an AD converter 27.
The controller 28 obtains a response value VL based on the measured voltage at the frequency f and a response value VH based on the measured voltage at the frequency 5f from the digital data, and calculates the ratio VH / VL. If there is no liquid leakage, the ratio VH / VL is used as the measurement electrode 2
The position of the tip 2a is detected, but the principle of its operation is disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 4-64354, so that the description in this specification is omitted.

FIG. 10 shows the value of the ratio VH / VL on the vertical axis and the distance from the tip 2a of the measuring electrode 2 to the apex on the horizontal axis as in FIG. Here, the solid line L ₁
Is in a state where saline is accumulated in the root canal and it is not leaking,
The broken line L ₂ illustrates the leaked state, the solid line M ₁ illustrates the state in which the mixed solution of the physiological saline and the drug solution (sodium hypochlorite) is accumulated in the root canal and is not leaked, and the broken line M _2. Exemplifies a leaked state. As shown in this figure, the ratio VH / VL has an upwardly convex shape, and the numerical value when there is liquid leakage is smaller than that when there is no liquid leakage.

The difference between the upper and lower portions corresponds to an abnormal portion of the response value due to the liquid leakage. Due to this difference, the response at the position corresponding to the apical stenosis portion, for example, 0.5 mm before the apex. The ratio of the values greatly differs between the case where there is liquid leakage and the case where there is no liquid leakage. Therefore, FIG.
As in the case of the above, a reliable measurement becomes completely impossible.

[0040] Turning now to the maximum value of the broken line, 0.84 at about 4mm short of the apex in L ₂ is 0.72 at about 5mm short of the apex in M ₂ is the maximum value, respectively. FIG. 11 shows the value of this maximum value as L ₂ in FIG.
And plots the respective divided by the numerical values of M _2, does it not utilize the ratio VH / VL outputted from the control unit 28 is performed a process of dividing a maximum value. This processing is performed by the control unit 28 switching to the compensation mode in the same manner as in the above example. The ratio of the portion showing the maximum value is converted to just 1.0, and the ratio of the other portions is converted to 1 or less. You.

In this example, the converted numerical value is used as the converted value of the present invention. As can be seen from FIG. 11, the reference value is set to 1.0, for example, 0.93 of the converted value.
The apical stenosis can be detected by using the vicinity as the determination value of the arrival determination, and the apex can be detected by using the vicinity of 0.88 as the determination value of the arrival determination. That is, also in this example, by switching to the compensation mode when there is liquid leakage, the apical stenosis and the apex can be appropriately detected. Here, each ratio value is divided by its maximum value using VH / VL, but the response value ratio is VL /
VH can also be used, in which case each ratio value is divided by the minimum value.

Also in this example, a selection switch 30a can be provided as shown by a broken line in FIG. 9 so that switching to the compensation mode can be performed manually.
Also, a determination value setting operation unit 30b may be provided as shown by a broken line, so that the determination value can be manually set as appropriate.

The above example is an apparatus for detecting the position of the tip of the measurement electrode by using the phase shift between the measured voltage and the measured current or the shift of a set of current waveforms, or two types of measurement having different frequencies. The present invention is applied to an apparatus that detects the position of the tip of the measurement electrode by using the ratio of the response values due to the voltage. The present invention uses the above-described difference between the response values in JP-A-2-297359. It can also be applied to the device of Japanese Patent Publication No.

It should be noted that an apparatus that detects the position of the tip of the measurement electrode using the phase shift between the measured voltage and the measured current or the shift of a set of current waveforms performs the above-described compensation according to the present invention. Then, the effect of the resistance included in the equivalent circuit is eliminated, and the compensation for the capacitance is performed. Therefore, theoretically, the abnormal part of the response value due to the liquid leakage can be completely removed, and it is considered that the compensation effect according to the present invention is greater than that of the apparatus using the response value ratio or difference.

[0045]

As is apparent from the above description, the apical position detecting device of the present invention detects the tip position of the measuring electrode from the change in the response value corresponding to the impedance between the measuring electrode and the oral electrode. In the apex position detecting device configured as described above, when the response value is affected by leakage of blood or a drug solution from a root canal, the abnormal portion of the response value caused by these fluid leaks is compensated. It is provided with compensating means for removing the influence, and compensation selecting means for switching to a compensation mode by the compensating means. Therefore, even if there is liquid leakage, there is no need to stop the measurement or clean the inside and outside of the teeth, and the work can be continued as it is, so that the burden on the operator is reduced, and highly reliable measurement is possible. In addition, medical treatment can be advanced efficiently.

If the compensation selection means is configured to detect an abnormal response value and automatically switch to the compensation mode, a device which does not require a mode selection operation and has good operability can be obtained. Further, in the case of switching to the compensation mode by manual operation, the control circuit is simple and the cost of the apparatus can be reduced.

The compensation means detects that the response value or the converted value obtained by performing a certain process on the response value has reached a maximum value or a minimum value, and a reference value is determined based on the maximum value or the minimum value. When the response value obtained subsequently or the converted value obtained by performing a certain process on the response value changes by a predetermined judgment value with respect to the reference value, the tip of the measurement electrode is apical or By configuring so as to determine that it has reached the vicinity, it is possible to surely perform the compensation operation for removing the abnormal response value due to the liquid leakage.

Further, in the case where the phase shift between the measured voltage and the measured current or the shift of a set of current waveforms is used as the response value, the effect of the resistance included in the equivalent circuit is eliminated to eliminate the electrostatic effect. The compensation operation for the capacitance can be performed more reliably.

Further, in the apparatus provided with setting means for arbitrarily setting a judgment value used for judging that the tip of the measuring electrode has reached the apex, the judgment is made according to the use conditions, the type of the chemical solution, and the like. By changing the value, it is possible to more appropriately remove a response value abnormality due to liquid leakage.

[Brief description of the drawings]

FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a signal waveform in the device.

FIG. 3 is a graph showing a relationship between a tip of a measurement electrode and a response value in the device.

FIG. 4 is a graph showing a relationship between a tip of a measurement electrode and a converted value in the device.

FIG. 5 is a graph showing a relationship between a tip of a measurement electrode and a response value in the same device.

FIG. 6 is a graph showing a relationship between a tip of a measurement electrode and a converted value in the same device.

FIG. 7 is a block diagram of an apparatus according to another embodiment of the present invention.

FIG. 8 is an explanatory diagram of a signal waveform in the device.

FIG. 9 is a block diagram of an apparatus according to still another embodiment of the present invention.

FIG. 10 is a graph showing a relationship between a tip of a measurement electrode and a ratio of a response value in the device.

FIG. 11 is a graph showing a relationship between a tip of a measurement electrode and a converted value in the above device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tooth 1a Root canal 1b Apical tip 2 Measurement electrode 2a Tip 3 Oral electrode 4,11,21,22 Measurement signal generation circuit 7,28 Control unit 8,29 Display unit 9,30 Compensation circuit 9a, 30a Switching operation unit 9b, 30b Judgment value setting operation section

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Kazunari Matoba 680 Higashihama-machi, Fushimi-ku, Kyoto F-term in Morita Manufacturing Co., Ltd. (reference) 4C052 AA06 FF07 LL07 NN02 NN03 NN16

Claims (9)

[Claims] An apex position detection device configured to detect a tip position of a measurement electrode from a change in a response value corresponding to an impedance between the measurement electrode and an oral electrode,
When the response value is affected by leakage of blood or a drug solution from the root canal, a compensation means for compensating for an abnormal portion of the response value due to the leak of the drug solution and removing the effect, and An apex position detecting device, comprising: a compensation selecting means for switching to a compensation mode by the compensating means. 2. The apex position detecting apparatus according to claim 1, wherein said compensation selecting means is configured to detect an abnormal response value and automatically switch to a compensation mode. 3. The apex position detecting device according to claim 1, wherein said compensation selecting means is configured to switch to a compensation mode by manual operation. 4. The compensation means detects that a response value or a converted value obtained by performing a certain process on the response value has reached a maximum value or a minimum value, and a reference value is determined based on the maximum value or the minimum value. When the calculated response value or the subsequent response value or the converted value obtained by performing a certain process on the response value changes by a predetermined determination value with respect to the reference value, the tip of the measurement electrode is apical. 2. The apex position detecting device according to claim 1, wherein the apex position detecting device is configured to determine that it has reached the vicinity thereof. 5. An AC measurement voltage is applied between the measurement electrode and the oral electrode, and a waveform of the measurement voltage is compared with a waveform of a measurement current flowing between the electrodes to determine a phase shift between the voltage waveform and the current waveform. The apex position detecting device according to claim 4, wherein the apex position detecting device is configured to set a response value as a response value. 6. Applying a measurement voltage as a set of at least two single-shot waveforms having different transient phenomena caused by impedance including a capacitance component between the measurement electrode and the oral electrode,
5. The apex position detecting device according to claim 4, wherein a deviation of a waveform of a set of measurement current flowing between both electrodes is set as a response value. 7. The method according to claim 5, wherein a minimum value of the response value is set as a reference value, and a value obtained by subtracting the minimum value from a response value obtained subsequently is set as a converted value. Apical position detection device. 8. Applying at least two kinds of measurement voltages having different frequencies between the measurement electrode and the oral electrode, calculating a ratio of response values at each frequency obtained between both electrodes, and determining a maximum value or a minimum value of the ratio. 5. The root according to claim 4, wherein a value obtained by dividing the value by the value is used as a reference value, and a value obtained by dividing a ratio of subsequently obtained response values by the maximum value or the minimum value is used as a converted value. Point position detector. 9. The apex position detecting device according to claim 4, further comprising a setting unit for arbitrarily setting the determination value.