KR100242068B1 - Frequency-dependent type apex locator - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency dependent electron canal length detector, and in selecting a frequency for a signal used in the canal length detector, to specify a frequency for measuring the canal length more precisely, and in particular, an error due to bleeding or other root canal cleaner, The present invention relates to a frequency dependent electron root canal detector that can be corrected using a difference.

According to the frequency-dependent root canal length detector according to the present invention, the frequency-dependent root canal length detector uses 400 kHz and 10 kHz when using frequencies of 500 kHz and 10 kHz (used in conventional root canal length detectors) or 300 kHz and 5 kHz. It is possible to measure root canal length more accurately than when using frequency, and is composed of oscillator, summing circuit, constant current circuit, probe and lip clip, demodulator, and analog divider (impedance ratio calculation) The root canal detector further includes a correction circuit for automatic correction using a voltage difference consisting of a differential amplifier, a comparator, a decoder, and a NAND gate, thereby minimizing errors in changes in the canal solution during root canal measurement. Root canal length can be detected.

Description

Frequency-dependent Electron Root Canal Detector

The present invention relates to a frequency-dependent electron root canal detector, in order to measure the root canal length more accurately by referring to the frequency used in the conventional root canal detector to select a specific frequency, in particular the error caused by bleeding or other root canal cleaner, such as voltage The present invention relates to a frequency-dependent electron root canal detector with a correction circuit added to enable correction using a difference.

For the success of root canal treatment, proper physicochemical cleaning should seal the root canal in three dimensions without damage to the root canal tissue. For this purpose, accurate root canal determination is important, and the limit of ideal root canal formation and filling is anatomically the lowest. This is the site of muscle stenosis. Accordingly, various experiments have been conducted to accurately measure the length of the root canal to accurately determine the length of the root canal. The various experiments are outlined as follows.

The method of measuring the length of the root canal has traditionally been an X-ray method, but after obtaining a wire inserted into the root canal, the relative length of the film is obtained. This method has the advantage of providing an approximate virtual structure image of the root canal, but first of all it takes a lot of time and it is difficult to make accurate measurements in severely curved root canals because it expresses three-dimensional images in two dimensions (Imao Sunada, ″ New Method for Measuring the Length of the Root Canal ″, JDRes., Pp 375-387, March-April, 1962).

The principle of the root canal detector was first published by Suzuki in 1942 and was not introduced into the clinic until the 1970s. The first method was to measure the resistance between the root canal and periodontal to find the apex of the root canal. This method is simple to use, but requires a calibration before use and has the disadvantage of drying the root canal (Imao Sunada, ″ New Method for Measuring the Length of the Root Canal, ″ JDRes., Pp 375-387, March-April, 1962).

In the early electron canal length detector developed by Sunada, when the reamer reached the periodontal membrane through the root canal, the electrical resistance between the reamer and the oral mucosa affected the patient's age and the shape of the tooth. Based on the theory that the diameter is constant regardless of the diameter of the canal, a measurement method using electrical resistance has been proposed. This saves the overall procedure time by making approximate measurements before radiography and allows for relatively accurate measurements even on teeth with curved root canals or abnormal root canals. However, this method maintained accuracy in relatively dry root canals, but tended to be shorter in the presence of bleeding or other conductive fluids such as root canal cleaners (Imao Sunada, ″ New Method for Measuring the Length of the Root Canal, JDRes., Pp 375-387, March-April, 1962).

In 1984, Ushiyama published a voltage gradient method that can accurately measure root canal length even in the presence of strong electrolytes in the root canal (J. Ushiyama, ″ New principle and method for measuring the root canal length). ″, J. Endo., 9: 97-104, 1983). This is a measure of the voltage drop along the root canal wall after the current flows in the root canal, the density of the current being highest in the root stenosis, the narrowest part of the root canal, and at the root canal area. It is a method of measuring root canal length based on the lowest theory. However, the use of a specially designed bipolar electrode was not appropriate in a narrow canal, and it was cumbersome and thus not widely used.

Then came the impedance method of measuring the change in electrical impedance in the apical region of the tooth. The principle of this method is that when the root canal is regarded as a small diameter and hollow tube, this material creates an impedance in the electrolyte. This method can be measured even in wet conditions using an insulated probe and has a high accuracy of 94.3%, but has the disadvantage of using an insulated probe and requiring accurate calibration before use.

Several methods have been developed to allow measurements even in the presence of an electrolyte solution in the root canal. In the case of Endocater (trade name), an insulation coated probe is used to compensate for this defect (NJ McDonald). and Eric J. Hovland, ″ An Evaluation of the Apex Locater Endocater ″, Journal of Endodontics, vol. 16, No. 1, pp. 5-8, Jan. 1990). However, this method has been shown to be able to measure even in a wet root canal in the presence of an electroconductive fluid, but the problem arises when the probe's insulating coating is damaged.

Among the measurement methods using impedance, Apit (trade name), then commercialized, measures the length of the root canal using the difference between two different signals. This makes it possible to measure even in wet root canals with electrolyte solutions and is not affected by the size of the file or the size of the apical foramen (T.Saito and Y. Yamashita, ″ Electronic Determination Of Root Canal LengthBy Newly Developed Measuring Device '', Dentistry in Japan, vol. 27, pp. 65-72, Dec., 1990). The biggest drawback of this method, however, is that it requires calibration every time the root canal is measured.

The recently developed detector (Root ZX) is frequency dependent and finds the apex as a ratio of two impedance values in the root canal obtained by applying two frequency signals simultaneously. It is easy to measure and can be measured whether the root canal is dry or wet without being affected by electrolyte in the root canal. In the apex foramen, a capacitance component is present in the apex foramen, resulting in an impedance between the electrodes due to the two frequency signals used. In the state where the pile is inserted, the ratio of the two impedances is constant at a specific position in the root canal. Since the impedance change in the dry and wet root canals is the same ratio, the impedance ratio due to the waveform of the two frequencies is calculated so that the accuracy of the measurement is not affected by the conditions in the canal. (J. Morita Corporation, Root ZX sales manual vol. 2) (C. Kobayashi and H. Suda, ″ New Electronic Canal Measuring Device Based On The Raio Method ″, Journal of Endodontics, vol. 20, No. 3, pp. 111-114, Mar. 1994).

In conclusion, the frequency-dependent detector method is the best in terms of ease of use and the effect of the endotracheal electrolyte. However, the frequency-dependent root canal detector differs in the frequency of the two signals used by the product. It is necessary to minimize the difference in the impedance ratio generated between the electrolyte solutions because there is a slight error in the contents or the incomplete root.

It is therefore an object of the present invention to specify two selective frequencies that can more accurately detect the root canal length in a frequency dependent root canal detector, and also the impedance generated between the electrolyte solution in the root canal when actually used in clinical practice in the frequency dependent root canal detector. In order to minimize the difference in the ratio to find the correct near-end hole in any solution state, to provide a frequency-dependent root canal detector with an automatic correction circuit that can be automatically corrected using the voltage difference.

1 is a block diagram schematically showing the overall configuration of a general frequency dependent root canal detector.

2A is a circuit diagram illustrating an oscillator and a summation circuit in a circuit diagram of a frequency dependent root canal detector according to the present invention.

2B is a circuit diagram illustrating a constant current circuit and a demodulator in a circuit diagram of a frequency dependent root canal detector according to the present invention.

2C is a circuit diagram illustrating an offset and a gain adjusting unit in a circuit diagram of a frequency dependent root canal detector according to the present invention.

2D is a circuit diagram illustrating a filter unit and a differential amplifier in a circuit diagram of a frequency dependent root canal detector according to the present invention.

Figure 2e is a circuit diagram showing a portion of the correction circuit of the circuit diagram of the frequency-dependent root canal detector including the correction circuit according to the present invention.

2F is a circuit diagram showing an output unit and an input power supply unit among circuit diagrams of the frequency-dependent root canal detector according to the present invention.

3 is a diagram illustrating a method for measuring root canal length by applying a frequency-dependent root canal detector according to the present invention to a tooth model.

Figure 4 shows the difference between the voltage value of the low frequency signal and the voltage value of the high frequency signal during the root canal measurement in the dental model experiment using a frequency-dependent root canal detector before the automatic correction using the impedance difference according to the present invention The figure which shows the result of recording a measurement error.

5 is a block diagram schematically showing the configuration of a correction circuit according to the present invention.

* Explanation of symbols on the main parts of the drawings

10. Oscillator 11.Summing circuit

12. Constant Current Circuit 13. Probe

14. Lip Clip 15. Demodulator

16,17. Voltage Measuring Unit 18. Analog Divider

19. Analog meter 20. Oscillator

21. Summing circuit 22. Constant current circuit

23. Demodulator 24. Offset and gain adjuster

25. Filter unit 26. Division operation unit

27. Differential amplifier 28. Correction circuit

29. Output section 30. Input power section

31. Apex locator 32. Probe

33. Lip Clip 34. File

35. Saline 36. Teeth

According to the present invention is used as an input signal in the frequency-dependent root canal detector consisting of an oscillator, summing circuit, constant current circuit, probe and lip clip, demodulator, analog divider (analog divider calculation) The root canal length detection experiment using different frequencies of the two signals is used to select the two frequencies with the smallest measurement errors.

According to the present invention, the measurement error is automatically corrected in addition to the frequency-dependent root canal detector consisting of an oscillator, a summation circuit, a constant current circuit, a probe, a lip clip, a demodulator, and an analog divider. A frequency-dependent root canal detector is provided that further includes a correction circuit consisting of a differential amplifier, a comparator, a decoder, and a NAND gate.

The present invention will be described in detail with reference to the drawings as follows.

The circuit of the frequency dependent root canal detector according to the present invention uses a frequency signal of 500 Hz and 10 Hz in the oscillator generating the sine wave according to the object of the present invention, and a correction circuit for automatically correcting the error caused by the electrolyte solution. 2A to 2C, the entire circuit includes the oscillator 20, the summation circuit / constant current circuit 21, the demodulator 22, the offset and gain adjuster 23, and the filter. A unit 24, a division operation unit 25, a correction circuit 26, an output unit 27, and an input power supply unit 28. The operation of this circuit will be described with reference to Figs. 2A to 2C, which are circuit diagrams of one embodiment of the present invention.

In the oscillator 20, as shown in FIG. 2A, the ICL8038 (Intersil) of U1 and U2 is a function generator that outputs high accuracy sinusoidal, triangular, and square waves, and also has a frequency band of 0.001 kHz to 300 kHz. Wide as The output waveform of the ICL8038 has the following frequencies.

In the case of U1, R1, R2, and C1 are external devices that determine the frequency. Adjust the resistance value when C1 = 1nF so that the desired sinusoidal wave of 10㎑ is generated. Variable resistors (R3, R6) and resistors (R4, R5) connected to pins 1 and 12 minimize the distortion of the sine wave. Pin2 is a sine wave, pin3 is a triangular wave, and pin9 is a square wave output. Here, only the output of the sine wave is adjusted to have a peak value of 1Vp using a variable resistor (R13). This signal is used as the input of the summing circuit after passing through the buffer and reduced to 400mVp by using a variable resistor, and is also used as a carrier signal of the demodulator.

In U2, adjust with C2 = 0.047㎌ and variable resistors R7, R8 so that 500 sine wave comes out.

Next, in the summing circuit 21, as shown in Fig. 2A, the signals of 500 Hz and 10 Hz, each having a peak value of 1 Vp, are summed and modulated at U5B via a 100 Hz resistance. This signal is a signal to be input through a file through a constant current circuit, and at this time, the output can be limited again by using a 100㏀ variable resistor which is a feedback resistor of U5B.

In the constant current circuit 22, U6 is used as a constant current circuit in FIG. 2B, and the current I _L flowing through the load in this circuit is caused by the voltages of the positive input (V ₊ ) and the negative input (V ₋ ) of the op-amp. It is determined as follows.

Output at this time is V _OUTPUT = 2V -V _{L -} a.

Therefore, if the negative input is grounded and the input is zero, the strength of the current flowing to the load is determined only by the magnitude of the positive input, and the output is a modulated signal that has passed through the constant current circuit. Therefore, after demodulating the voltage changes of the two frequency signals obtained at this time, the ratio is obtained as the impedance ratio.

The intensity of the current flowing through the pile to the load is less than 10kV even when the peak value of the input signal is 1Vp when R = 100kV. The output signal of U6, which is twice as large as the modulated signal, passes through the low pass filter and the high pass filter to remove noise, passes through a buffer, and then inputs each demodulator.

Lowpass Filter Cutoff Frequency:

High pass filter cutoff frequency:

In the demodulator 23 of FIG. 2B, the signal modulated by the MC1496 (U7, U8) is demodulated, and a change in voltage is output for each of two frequencies. In this case, the carrier signal passes the sine wave finally obtained by ICL8038 through the variable resistor, respectively, to generate a signal of 400㎷p at U3B and U4B. The output voltage is determined in proportion to the product of the input signal and the carrier signal. The gain of the circuit is determined by the resistors Re (R30 and R41) and the external resistors R _L (R34, R35, R45 and R46).

In the offset and gain adjuster 24 shown in Fig. 2C, since the output of the demodulator has a different gain for each frequency, it is necessary to adjust the output so that the output is the same when the load is connected only with pure resistance. First, adjust the offset of each output voltage with the variable resistors R50 and R60 so that the output voltage is '0' when the resistance component of the load is '0', and then the output voltage is 10V when the variable resistor connected to the load is 10㏀. Adjust the gain using R53 and R63 so that In this case, it is important to adjust the two output voltages when the resistance is connected to the load.

Next, the filter unit 25 shown in FIG. 2D removes noise and distortion generated by the signal output from the demodulator through offset adjustment and amplification by a low pass filter. The cutoff frequency is as follows.

In the division operation unit 26 of FIG. 2D, U13 (MPY100) is used to use a division operator to obtain a ratio of voltages of two signals obtained through the demodulator. The device can multiply, divide, square, or square root with differential inputs. The output at the circuit connection for division is In this case, Z1 = X2 = Y1 = 0, and the voltage change of the 500 kHz signal is X1 and the voltage change of the 100 kHz signal is Z2 so that a value 10 times the impedance ratio of the two signals is output.

In the correction circuit 28 shown in FIG. 2E, two signals obtained through the demodulator 23, the offset and gain adjuster 24, and the filter unit 25 are converted into two signals through the differential amplifiers U14 and 27. Find the voltage difference (VL-VH). The signal is used as the positive and negative inputs of the comparator LM358, and the comparator operation is performed using the voltages 2.4V and 0.6V respectively obtained by voltage distribution using R72, R73, and R74 as different inputs. The comparator output is voltage-distributed for use as the next digital signal input. Accordingly, the input of the decoder 74LS139 is shown in Table 1 according to the voltage difference, and the output thereof is shown in Table 2.

Voltage difference range Input of decoder A B 2.4V or more H L 0.6V-2.4V L L 0.6V or less L H

Truth table of decoder (74LS139) Enable (1) A (2) B (3) Y0 (4) Y1 (5) Y2 (6) Y3 (7) H X X H H H H L L L L H H H L H L H L H H L L H H H L H L H H H H H L

The outputs Y0, Y1, Y2, and Y3 of the decoder cause only one output to be high in each voltage range through the NAND gate. The correction signal is obtained by summing up the voltage in U19B (U19D). The feedback resistance of U19D is fixed, and the input gain is changed by varying the input resistance according to each output according to the voltage difference range. The final output of the correction signal (No. 14 of U19D) should be adjusted to 0 when the voltage difference range is 0.6-2.4V by adjusting the variable resistor R85 of U19B, + 0.8V when below 0.6V, and -0.8V above 2.4V. Comes out.

In the correction circuit 28, a result obtained by summing the correction value obtained through the comparator by the impedance ratio and the voltage difference obtained by the MPY100 is output from the output unit (analog meter) 29. To adjust the scale of the result, a variable resistor is used to adjust the offset (R93) and the gain (R92).

The power supply of the entire circuit is separated from the input power supply unit 30 using a DC-DC converter.

The frequency-dependent root canal detector according to the present invention configured as described above is an impedance measuring device, which is basically an oscillator 10, a summation circuit 11, a constant current circuit 12, a probe (as shown in FIG. 1). A probe 13, a lip clip 14, a demodulator 15, and an analog divider 18 (corresponding to the impedance ratio calculation in FIG. 1). As a waveform to be used, a constant voltage waveform is obtained using ICL8038 (function generator), and the current flowing to the teeth is limited to 10 μA or less using the constant current circuit 12. As described in the above circuit configuration, the demodulator 15 obtains a voltage value by using a balanced demodulator to remove the oscillation frequency, and the ratio of the two voltage values through the constant current circuit through the analog divider 18 becomes the impedance ratio. The impedance ratio is calculated by setting the scale of the analog divider 18 to 10, and the result of the correction circuit using the voltage difference between the two signals is added to the result, and the output is displayed by the scale of the meter.

The lower the measurement frequency, the greater the influence of the pile thickness on the impedance level. Therefore, in order to reduce the measurement error according to the file size, it is better to measure more than several micrometers.

As a result of measuring the change of the impedance according to the depth of the root canal probe, the impedance range near the apex in the frequency range of 400 ㎐ to 11 ㎑ was measured from 2 ㏀ to 7 ㏀. The ratio of impedance is calculated as the ratio of measured voltages, and in order to be used as an op-amp signal, the voltage value of two signals should be set at the same time to be changed within the range of 0V to 10V. It should be set so as not to degrade the division operation.

In order to satisfy this condition, a low frequency signal was set within 1 kHz, and a high frequency signal was set within 10 kHz, and one of them was selected as the same frequency as a conventional product.

The frequency used in the present invention among 400 Hz / 8 Hz and 300 Hz / 5 Hz and 500 Hz / 10 Hz, which is a frequency used in the conventional frequency-dependent root canal detector, will be described below. The experiment shows whether the improved effect is as follows.

The root canal length of the dental model 36 immersed in saline 35 is measured using the root canal detector 31 configured as shown in FIG. 1, as shown in FIG. 3.

The total number of teeth to be measured is 7 to 11 root canal lengths. First, the root canal length expected in the 11 roots was measured, and the impedance ratio was measured at 0.5 mm intervals at a depth of ± 2 mm. At this time, the types of frequencies used in the experiments are 400 kHz and 8 kHz, 300 kHz and 5 kHz and newly specified 500 kHz and 10 kHz, which are used by the existing equipment Root ZX (Morita).

This resulted in the change of the impedance ratio according to the root canal length at each selected frequency and the ratio value at the apex was determined.

Next, the ratio obtained at each selected frequency was defined as the root position, and the root canal length was measured. At this time, the measurement results were obtained by repeatedly measuring 11 root canals five times, and then the error was calculated.

As a result, the impedance ratio and the change in impedance near the root point of each of the three selected frequencies were measured as shown in Table 3 and the graph below.

Impedance Ratio at Apex Selectable frequency Impedance Ratio at Near Point (× 10) One 300㎐ / 5㎑ 6.01 2 400㎐ / 8㎑ 5.08 3 500㎐ / 10㎑ 6.51

Comparison of Impedance Ratios with Probe Depth for Three Frequency Cases

Using the impedance ratio value obtained here, the file was inserted to the point indicating the corresponding ratio, and then the length of the file was measured to obtain an error from the expected length. In this experiment, 55 measurements were made of 11 root canals five times, and the average error is shown in Table 4 below.

Selectable frequency error(%) One 300㎐ / 5㎑ 1.502 2 400㎐ / 8㎑ 1.197 3 500㎐ / 10㎑ 0.877

In the above results, first, all three selected frequencies showed about 1% error, which was evaluated as an excellent apex locator, but among them, the error was smallest when selecting 500㎐ and 10㎑. In the graphs, the impedance change of the three cases shows the largest slope at 500 ㎐ and 10 근 at the near point. If the range between frequencies is wide, the change in impedance ratio is large. The range of lengths indicated is reduced, so there is less error. Therefore, three frequencies were used to obtain the most accurate measurement of the root canal length. Two frequencies of 500 Hz and 10 Hz were obtained.

Next, referring to the configuration of the correction circuit shown in FIG. 2C, a correction circuit according to the present invention for automatically correcting an error with respect to an impedance difference between two signals caused by a change in the electrolyte solution in the root canal will be described as follows. same.

First, the principle of the frequency dependent root canal length detector will be briefly described. The frequency dependent root canal length detector calculates an impedance ratio obtained by simultaneously applying two AC signals, and the detector is shown in FIG. And a summation circuit 11, a constant current circuit 12, a probe 13, a lip clip 14, a demodulator 15, and an analog divider 18. As described with reference to FIG. 1, the reason why the measurement method using the impedance ratio is not influenced by the electrolyte such as bleeding or the root canal detergent is as follows. Because it is the same. In other words, the impedance in the dry root canal is multiplied by the following constant to obtain the impedance in the wet root canal.

C: coefficient according to electrolyte Water = 1 Blood ≒ 2/3 Sodium Hypochlolite ≒ 1/2

Z _low : Impedance of low frequency signal

Z _high : Impedance of high frequency signal

At this time, the impedance in the root canal is caused by the presence of capacitance in the root canal when the root canal is viewed as a thin and long tube. The higher the frequency, the lower the impedance. Therefore, the two impedance ratios always have a value of Z _high / Z _low <1. Using this property, the impedance ratio of the two signals is obtained as in Equation 2, and the effect of the solution in the root canal can be reduced and the constant value can be always maintained at a specific position in the root canal.

On the other hand, since the voltage difference between the two signals depends on the conductivity of the solution, the measuring instrument using this method requires zero adjustment for every measurement. That is, the value of the voltage difference will be higher in physiological saline in a solution with low conductivity (H ₂ O ₂ ), and smaller in physiological saline in a solution with high conductivity (NaOCl). As described above, the frequency-dependent root canal detector using the impedance ratio is not affected by the solution, but since the error is substantially generated in the clinic, the measurement error is corrected based on the distribution of the change in the root canal solution and the measurement error. Can be reduced. In the conventional frequency-dependent root canal detector for this automatic correction, in order to determine the effect of the detector further including the correction circuit according to the present invention, the detector including the correction circuit described in the circuit configuration of FIG.

The root canal length of the tooth in the tooth model in which the tooth extracted as shown in FIG. 3 is fixed to an acrylic barrel by using a root canal length detector configured as shown in FIG. 1 and filled with gauze soaked in saline. The measurement was made.

In order to investigate the effect on the change of electrolyte solution in the root canal, H ₂ O ₂ and NaOCl, which are used in the clinical use as a canal cleaning agent and can affect the endotracheal conductivity with bleeding, were respectively tested. Here, H ₂ O ₂ is a solution having a lower conductivity than physiological saline, and NaOCl is a solution having a high conductivity.

The basic theory is that the frequency-dependent electron root canal detector has no change in impedance ratio because the rate of change of the two impedances is the same depending on the solution. For the 21 root canals of 9 teeth, three measurements were taken in saline, three times in H ₂ O ₂ and two times in NaOCl.The error was 0.06 ± 0.135mm in saline, 0.41 ± 0.201mm in H ₂ O ₂ , In NaOCl, the error is –0.25 ± 0.271mm, sometimes out of clinical tolerance (± 0.5mm). The measurement error is the distance from the measured root canal of the extracted tooth by 0.5mm to the distance to the muscular stenosis, and it is displayed as '-' for short measurements and '+' for long measurements. .

The data for the total results were averaged by the number of repeated measurements, and 21 data from each solution were used to verify the significance level of 0.005 by ANOVA one-way classification. The results showed that p <0.005 was affected by each solution. However, if most of these effects are within the clinical tolerance (± 0.5mm), there may be no problem. An attempt was made to automatically correct the voltage difference.

The configuration of the automatic correction circuit according to the present invention for automatic correction is shown in FIG. 2C, which is basically a differential amplifier (U14) 27, a comparator (LM358), a decoder (74LS139), a NAND gate. (U18A, U18B, U18C, U18D). This is simply illustrated in FIG. 5.

The experiment is performed by the correction circuit as automatic correction using the voltage difference, which will be described in detail as follows. 4 is a detector manufactured based on the basic principle of the frequency-dependent root canal detector, and measured according to each solution without adding a correction circuit. (For 21 root canals, saline and H ₂ O ₂ are twice, and NaOCl is 1). Is the result of recording the voltage value V _H of the high frequency signal, the voltage value V _L of the low frequency signal, and the measurement error at that time. At this value, each voltage changes according to the conductivity of the solution. Instead of distinguishing the state of the solution by the distribution of the voltages, the relationship between the difference and the error between two voltages with small deviations is used. Referring to the results shown in FIG. 4, the voltage difference is large in the solution having low conductivity based on the saline solution, and the voltage difference is small in the solution having high conductivity. Therefore, the voltage difference can be used to represent the electrolyte state of the solution. The magnitude of the measured voltage value and the difference may vary depending on the amplification degree of the signal.

When the impedance bigap in saline have been called Q _S, and hold the impedance ratio Q _H of the H ₂ O ₂ is measured is because it will be the ratio of a value greater than Q _S at the same point when the condition receiving much influence of H ₂ O ₂ bigap It is possible to measure by outputting to some extent and output, and to measure the impedance ratio Q _N of short measured NaOCl at the same point, the ratio will be smaller than Q _S. It was made to measure. At this time, the impedance ratio to be measured was experimentally confirmed that the point of the stricture when pointed to 0.6 in saline, and the scale shown on the actual meter is 6.0 times 10.

In this case, any value added to or subtracted from the impedance ratio Q _H and Q _N cannot be corrected by satisfying all conditions because the impedance ratio and distance in the root canal do not linearly match for each root canal, but only operate on values that deviate much from the error. It is set to. When the conductivity is high or very wet, we add random values to the output impedance ratio to reduce the short measurement by inserting the pile further to the point where the impedance ratio is 6.0. When the conductivity is small or very dry In order to reduce the length of the measurement by subtracting a random value from the output ratio value, the file has to be inserted less in order for the impedance ratio to be 6.0. When the experiment for the three solutions as described above was added again by adding a correction circuit configured as shown in FIG. 5, an improved result was obtained as shown in Table 5 below.

Brine H ₂ O ₂ NaOCl Before correction After correction Before correction After correction Before correction After correction Average (mm) 0.00 0.42 0.32 -0.34 -0.12 Standard Deviation 0.14 0.18 0.19 0.30 0.20 accuracy(%) 100 Reference price 75 90 80 100

At this time, there were 21 root canals in each solution group. The length of the root canal measured in the above experiment was -0.5mm from the measured root canal length of the extracted tooth, and the length was compared with the present value as the distance to the stenosis. The accuracy is regarded as valid when it is within the range of ± 0.5mm, and when the error with the measurement length is within. From these results, the error measured by the existing equipment was influenced by the solution (p <0.005), but the accuracy was calculated as a percentage by applying the clinical tolerance, and it was relatively relatively 86% regardless of the solution. Came out high. However, the measurement result of adding the circuit which is automatically corrected by using the impedance difference according to the present invention was very accurate, which was 97%. First of all, the paired T-test was used to evaluate the results of H ₂ O ₂ and NaOCl before and after the calibration using p-0.0078 and p = 0.0008, respectively.

Therefore, the measurement error can be reduced by automatically calibrating the root canal state by using the impedance difference indicating the state of the root canal electrolyte in the root canal measuring instrument which minimizes the influence of the electrolyte solution in the root canal by using the impedance ratio.

As described above, for the success of the root canal treatment, it is important to accurately determine the root canal length and thus accurately measure the length of the root canal. According to the frequency-dependent root canal detector according to the present invention, using frequencies of 500 Hz and 10 Hz, The error is reduced compared to the 400 ㎐ and 8 주파수 frequencies or 300 ㎐ and 5 주파수 frequencies used in conventional detectors, so that the root canal length can be measured more accurately.The oscillator, the summation circuit, the constant current circuit, and the probe And a correction circuit composed of a differential amplifier, a comparator, a decoder, and a NAND gate in the frequency-dependent root canal detector consisting of a lip clip, a demodulator, and an analog divider. By automatically calibrating the measurement error with the voltage difference, the root canal length can be detected more accurately.

Claims (2)

Frequency dependent type consisting of oscillator 10, summing circuit 11, constant current circuit 12, probe 13 and lip clip 14, demodulator 15, analog divider 18 In the root canal detector, The root canal detector, characterized in that the oscillator uses a frequency of 500 Hz and 10 Hz to measure the impedance. In the frequency dependent root canal detector consisting of an oscillator, a summation circuit, a constant current circuit, a probe, a lip clip, a demodulator, and an analog divider, Comprising a differential amplifier (U14) (27), a comparator (LM358), a decoder (74LS139), NAND gates (U18A, U18B, U18C, U18D), and further includes a correction circuit 26 for automatically correcting using the voltage difference Frequency-dependent root canal detector, characterized in that configured to minimize the measurement error.