JPH0497745A - Dental detector for detecting position of apical foramen - Google Patents

Abstract

PURPOSE:To achieve a zero adjustment automatically while a measuring needle is inserted into a root canal in the detection of the position of an apical foramen by inserting the measuring needle simply thereinto the keep the needle as it is until an alarm sound is heard. CONSTITUTION:At the moment when a comparator 33 detects an output voltage of a differential detection circuit 31 being zero or after a time set with a timer 41 passes, an alarm 42 is actuated to inform of the end of a zero adjustment. After the checking of the alarming, as a measuring needle is further inserted, a reading of an indicator 43 rises gradually according to a difference of voltage generated between input terminals (a) and (b) of a differential detection circuit 31, and reaches a specified position shown on a display section. The position shown corresponds to the position of the apex of the root. A value of the position is common to all human beings irrelevant to personal difference. Therefore, when a pointer of the indicator reaches the position, a tip of the measuring needle 3 is considered as reaching the position of the apical foramen. A length of insertion of the measuring needle at this moment is measured, thereby enabling the learning of a length of a root canal.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apical foramen position detection device used in dental treatment;
More specifically, the present invention relates to zero point adjustment in the apical foramen position detection device.

In dental treatment, we enlarge, clean, and disinfect root canals.1
Next, by filling the root canal with a filling material and performing root canal treatment, it is possible to treat the patient's daily living without having to extract the tooth. This root canal treatment requires accurate detection of the position of the end of the root canal (hereinafter referred to as the apical foramen).

For example, as a device for electrically detecting the position of the apical foramen,
What is described in Japanese Patent Application Laid-Open No. 60-174144 is
As shown in FIG. 4, a reamer 3 is inserted as a measuring needle into the root canal 2 of a tooth 1, and two electrodes of, for example, IK 72 and 5 KHz are inserted between it and a single electrode 5 in contact with the oral mucosa 4. The position of the apical foramen 6 is detected by applying an alternating current voltage of two frequencies. 10 is a pulse generator that generates two different frequencies, and this pulse generator 1o is connected to the measuring needle 3 and the single electrode 5, respectively. A resistor 11 is connected between the single electrode 5 and the pulse generator 10, and both ends thereof are connected to amplifiers 12 and 13, respectively. The output of the amplifier 12 is connected to a filter 14 for 5 KHz, and this output is rectified by a rectifier circuit 15 and connected to one input terminal of a comparator $16. Further, the output of the amplifier 13 is connected to a filter 17 for 1 kHz, and this output is rectified by a rectifier circuit 18 and connected to the other input terminal of the comparator 16. The output of this comparator 16 is connected to an amplifier 19, and the output thereof is connected to a display device 20.

FIG. 5 is a diagram showing the outputs of points a and b, indicated by X marks in FIG. 4, with the position of the measuring needle 3 in the root canal 2 plotted on the horizontal axis. In the circuit configuration shown in FIG. 5, it is assumed that the fundamental generation frequency of the pulse generator 10 is set to IKHz. Now, the dentist slowly inserts the measuring needle 3 into the root canal 2.

At this time, the pulse generator 10 multiplexes the IKHz impulse signal and the 5KHz impulse signal at a predetermined period and outputs the multiplexed signal. This output signal and the measuring needle 3 and single electrode 5
A weak current in response to the impedance between the resistor 1
1, and this weak current is amplified by amplifiers 12 and 13, respectively.

Of these, only the one that responds to the impulse signal of IKI (z) passes through the filter 17, and the output at point a (Figure 4) is as shown by a in Figure 5.Similarly, the one that responds to the impulse signal of 5KHz passes through the filter 17. Only the signal passes through the filter 14, and the output at point b (FIG. 4) is as already shown in FIG.

That is, while the measuring needle 3 moves inside the root canal 2, the measuring needle 3
The impedance between the electrode 5 and the single electrode 5 is substantially constant, and the outputs at points a and b in response to each frequency of the human input signal are output in a substantially linear manner, as shown by range I in FIG. In this state, the impedance between the measuring needle 3 and the single electrode 5 decreases near the point where the measuring needle 3 moves out from inside the root canal 2.

In response to this change in impedance, the outputs at points a and b increase, but due to the frequency characteristics, output a changes slowly and output A changes quickly, as shown in range 3 in FIG.

Here, if we focus on the difference between both outputs a and b, the rate of change of outputs a and b differs depending on the frequency characteristics for each human power frequency, but this rate of change is greatest near the apical foramen 6, so both outputs a The point where the difference between and b is the minimum is detected as the position of the apical foramen 6.

In order to detect the position where the difference is minimum in this way, it is not possible to find the exact minimum point unless the measuring needle 3 is advanced beyond the position of the apical foramen.

However, advancing the measuring needle beyond the position of the apical foramen is problematic, and the measuring needle often penetrates the root canal.

In order to solve the above-mentioned problems, the applicant first
We proposed a dental apical foramen position detection device that can accurately detect the apical foramen position by detecting that the differential output has reached a specific value.

Referring again to FIG. 5, the operating principle of the apical foramen position detection device proposed earlier by the present applicant will be explained. In FIG. is the output signal. Here, a voltage a' corresponding to the difference from b in region I is applied to a as a bias value. Then, in region I, a
The values of and b become equal, and in region (■), a becomes a'', b becomes b', and the difference between the two changes as the measuring needle 3 advances. Clinical data shows that the value of the difference between a' and b' at the position corresponding to the minimum value of the difference between It was discovered that the results are almost the same.

As a result, by adding (or subtracting) the difference in region I to the output signal of one frequency as a bias value, both values in region I are made equal, and the output value of the circuit that detects the difference is set to a predetermined constant value. It was found that it is possible to determine the position of the apical foramen at the time when the value is reached.

FIG. 6 shows the circuits below comparator 16 in FIG.
2 is an amplifier, 23 is a display, 24 is a storage circuit, 25 is an erasing circuit, and 26, 27 and 28 are pulse generators. IK
The output signal with a frequency of Hz is applied to terminal a, and the output signal with a frequency of 5 to 7 is applied to terminal 2, and the output voltage of the difference is obtained by an adder/subtractor 21, which is displayed on a display 23 via an amplifier 22. Ru. The memory circuit 24 is the pulse generator 2
The output value of the amplifier 22 is stored by the storage pulse from 6, and is reset by the signal from the erase circuit 25. Pulse generator 27 generates an erase pulse that drives erase circuit 25 . The pulse generation circuits 26 and 27 are activated based on a reset pulse from the pulse generator 28 when the reset switch 29 is pressed, but as shown in FIG. 7, the storage pulse is generated subsequent to the erase pulse. . The stored value of the storage circuit is applied to one input, for example, input terminal a, as a bias value.

FIG. 8 is a diagram for explaining the operation of FIG. 6, and in the figure,
(■) indicates a display section, and (n) indicates an adder/subtractor section. (,)
The figure shows the start point, in which case the stored value from the memory circuit 24 is O, and when a voltage value of 2 is applied to the terminal a and a voltage value of 3 is applied to the terminal a, the output of the adder/subtractor 21 becomes 1. If the reset button 29 is pressed here, the memory circuit 24 is reset (in this case, since it is O, there is no change), and then the difference 1 is stored. This is the state shown in Figure (b), where 1 is added to terminal a as the bias value, so the output of the adder/subtractor 21 becomes O. As the measuring needle 3 advances, it moves from region ■ to region ■, and when the above-mentioned difference reaches a constant value, here a value of 5, it can be seen that the position of the measuring needle 3 has reached the apical foramen ((C) figure ). The next detection will be as shown in Figure (d), but if the condition of the root canal or the patient changes, the initial value will not necessarily be the same as in Figure (a). That is, as shown in (d), terminal a is 3. If the terminal is 6, the output of the amplifier 22 will be 2 since the memory circuit 24 stores 1. When the reset button 29 is pressed here, the erasing circuit 25 is driven by the erasing pulse, and the memory circuit 24 is first reset to O as shown in FIG. A storage pulse following the erase pulse sets storage circuit 24 to store this difference 3. Therefore, (f
) As shown in the figure, a bias value of 3 is applied to terminal a,
(g) The position of the apical foramen can be detected when the display shows 5 as shown in the figure. In addition, in FIG. 8, in order to simplify the explanation, the constant value is set to 5, but the value 5 has no meaning, and in reality, a mark is attached to the position corresponding to the constant value. When the meter needle reaches that position, it will be considered as the apical position.

As mentioned above, according to the invention previously proposed by the applicant, the position of the apical foramen can be detected at the point in time when the difference in output based on two frequencies becomes a constant value. The position of the apical foramen can be detected more appropriately than the one that detects the value, but the reset button must be pressed each time to detect the position of the apical foramen, making it very difficult to operate. It was bad.

In addition, the present invention solves the drawbacks of the apical foramen position detection device previously proposed by the applicant as described above, and enables the outputs of a and b to be output without pressing the reset button as described above. The purpose of this invention is to provide an apical foramen position detection device that can automatically perform zero adjustment.

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention uses two types of different frequency signals in an apical foramen position detection device that detects the apical foramen position by impedance change between a measuring needle and a single electrode. an oscillation circuit that generates a signal, a detection circuit that detects the impedance change in response to each of the frequencies, a difference detection circuit that successively compares each output of the detection circuit and outputs a difference, and an output of the difference detection circuit. a feedback circuit that feeds back and adds (or subtracts) to one input of the cough difference detection circuit to make the output of the difference detection circuit 0, and an alarm means for notifying that the output of the difference detection circuit has become 0. and a display means for notifying that the output of the difference detection circuit has reached a predetermined value. Hereinafter, the present invention will be explained based on examples.

FIG. 1 is a block diagram for explaining one embodiment of the present invention, in which 31 is a difference detection circuit, 32°, 33.34 is a comparator, 35.36 is a one-shot trigger (mono-multi) circuit, 37 flip-flop circuit, 38 pulse oscillator, 39 counter, 40 D/A converter, 41
The timer 42 is an alarm. 43 is an indicator.

Figure 2 is a diagram showing the relative positional relationship between the measuring needle and the root canal.
In the figure, Z3 is the position before inserting the measuring needle into the root canal, and Z2 is the position before inserting the measuring needle into the root canal.
zl is the measurement range where the measurement needle is inserted into the root canal and the O adjustment described below is performed, and zl is the measurement range where the measurement needle is inserted from the 0 adjustment position toward the root apex after the O adjustment described above is completed. , Zo is the apical foramen position.

FIG. 3 is a time chart for explaining the operation of the present invention, and FIG. 3(a) shows the relationship between each position of the measuring needle and the output signal of the difference detection circuit 31 at each position. Hereinafter, an embodiment of the present invention will be explained with reference to FIG.

First, considering the state before the measuring needle 3 is inserted into the root canal 2, at this time, the surface input voltages to the difference detection circuit 31 are equal, and therefore the output voltage of the difference detection circuit 31 is 0.
It becomes.

When the measuring needle 3 is inserted into the root canal 2 from this state, a voltage corresponding to the intra-root canal impedance appears at the input terminals a and b of the difference detection circuit 31 according to the respective frequencies. In this way, the output voltage of the differential detection circuit 31 is such that the first comparator 32 detects the change in the differential voltage between before and after the measuring needle 3 is inserted into the root canal 2, as shown in FIG. , (b)), When the differential voltage exceeds the threshold value (TH□) of the comparator 32, the one-shot trigger (mono-multi) circuit 35 is activated (Fig. 3, (c)), and its output signal activates the flip-flop circuit 37. Figure 3, (
d)), whose output activates the pulse oscillator 38 (Fig. 3,
(e)) The output pulses of the pulse oscillator 38 are integrated by a counter 40 (FIG. 3, (f)), and the integrated force is converted into an analog quantity by a D/A converter 40 and sent to one input terminal of the difference detection circuit 31. When the output voltage of the difference detection circuit 31 becomes 0, the second comparator 33 is activated (see FIG. 3).

(g)), one-shot trigger (mono-multi) circuit 3
6 is activated (Fig. 3, (h)), the flip-flop circuit 37 is inverted (Fig. 3, (d)), the pulse oscillator 38 is stopped (Fig. 3, (e)), and the integration of the counter 39 is stopped. However, the counter 39 holds the integrated value (FIG. 3, (f)). With this comparator 33, the difference detection circuit 31
At the same time as detecting that the output voltage has become 0, or after the time set by the timer 41 (see Fig.
)), the alarm 42 is activated to notify that the zero adjustment has been completed. After confirming this alarm, when the measuring needle 3 is further inserted, the indicator 43 displays.

Depending on the voltage difference generated between the input terminals a and b of the difference detection circuit 31, the voltage gradually rises and reaches the predetermined position V, (AP) displayed on the display (Fig. 3, (a) ). This display position is a display position corresponding to the root apex position, and this value V. (AP) is a value common to all people, regardless of individual differences. Therefore, when the pointer of the indicator reaches this position, it can be assumed that the tip of the measuring needle 3 has reached the position of the apical foramen (2,). By measuring the insertion length L of the measuring needle 3 at this time, the root canal length can be determined. After that, when the measuring needle 3 is pulled out through the root canal 2, the output voltage of the differential detector 31 will indicate the output voltage of the D/A converter 40, or the change in the input terminal at that time (Fig. 3, ( k)) is detected by the third comparator 34 (Fig. 3, (1)), and the counter 39 is reset by its output (Fig. 3, (f)), returning to the initial state (Fig. 3, (f)).
Figure, (a)).

As is clear from the above explanation, according to the present invention, when detecting the position of the apical foramen, the measuring needle is simply inserted into the root canal, and the alarm is emitted for a while. until I heard
If this state is maintained, O adjustment will be automatically performed during that time, making it possible to provide a root canal length measuring device that is extremely easy to use.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the main part configuration for explaining one embodiment of the present invention, FIG. 2 is a diagram showing the relative positional relationship between the measuring needle and the root canal, and FIG. 3 is a detailed diagram of the present invention. FIG. 4 is a configuration diagram for explaining an example of a conventional root canal length measurement device, FIG. 5 is a diagram for explaining its operating principle, and FIG. 6 is a diagram for explaining the principle of operation. FIG. 7 is a block diagram for explaining an example of the root canal length measurement device previously proposed by the applicant, and FIG. 8 is a diagram showing pulse signals that operate the storage circuit and erasing circuit shown in FIG. 6 is a diagram for explaining the operation of the root canal length measuring device shown in FIG. 6. FIG. 1...Tooth, 2...Root canal, 3...Measuring needle, 4...
・Oral mucosa, 5... Single electrode, 6... Apical foramen, 10.
...Pulse generator, 11...Resistor, 12.13...
Amplifier, 14.17 Filter, 15... Rectifier circuit, 1
6...Comparator, 19...Amplifier, 20...Display device, 21...Adder/subtractor, 22...Amplifier, 23...Display device, 24...Memory circuit, 25...Elimination circuit ,26,2
7.28... Pulse generator, 31... Difference detection circuit, 32, 33.34... Comparator, 35.36.
...One-shot trigger circuit, 37...Flip-flop circuit, 38...Pulse oscillator, 39...Counter, 40...D/A converter, 41...Timer, 42...Alarm, 43 ···Indicator. Figure 1 Figure 3 Figure 2 ←-------23 Location Figure 2? Figure A: Erasing pulse - Low storage pulse −[]−

Claims (1)

[Claims] 1. An apical foramen position detection device that detects the apical foramen position by impedance change between a measuring needle and a single electrode, comprising: 2
an oscillation circuit that generates different types of frequency signals, a detection circuit that detects the impedance change in response to each of the frequencies, and a difference detection circuit that successively compares each output of the detection circuit and outputs a difference; Feedback the output of the difference detection circuit to one input of the difference detection circuit and add (or subtract)
a feedback circuit for setting the output of the difference detection circuit to 0; an alarm means for notifying that the output of the difference detection circuit has become 0; and a display for notifying that the output of the difference detection circuit has reached a predetermined value. 1. A dental apical foramen position detection device, characterized in that it has means. 2. The output of the difference detection circuit activates the feedback circuit when the measuring needle is inserted into the root canal, sets the output of the difference detection circuit to 0, and generates the alarm; 2. The dental apical foramen position detection device according to claim 1, wherein the predetermined value is indicated when the apical foramen is inserted to the apical foramen position. 3. The feedback circuit has a pulse generator and a counter that adds the output pulses of the pulse generator, and the integrated value of the counter is fed back to one input terminal of the difference detection circuit, and the integrated value of the counter is fed back to one input terminal of the difference detection circuit. The dental apical foramen position detecting device according to claim 1 or 2, wherein the oscillation of the pulse generator is stopped when the output becomes zero.