JP2590300B2 - Dental apex position detection device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an apical hole position detecting device used for dental treatment, and more particularly, to zero point adjustment in an apical hole position detecting device.

2. Description of the Related Art In dental treatment, enlarging, cleaning, disinfecting a root canal, and then filling the root canal with a filling material to perform a root canal treatment, thereby treating a living tooth without tooth extraction. Have been. In this root canal treatment, it is necessary to accurately detect the position of the end of the root canal (hereinafter, apical foramen).

As a device for electrically detecting the position of the apical hole, for example, a device described in JP-A-60-174144 is described in US Pat.
As shown in the figure, a reamer 3 is inserted into a root canal 2 of a tooth 1 as a measuring needle, and an alternating current of two frequencies, for example, 1 KHz ₂ and 5 KHz is applied between the reamer 3 and one electrode 5 in contact with an oral mucosa 4. A voltage is applied to detect the position of the apical hole 6. Reference numeral 10 denotes a pulse generator for generating two different frequencies. The pulse generator 10 is connected to the measuring needle 3 and the single electrode 5, respectively. A resistor 11 is connected between the one electrode 5 and the pulse generator 10, and both ends of the resistor 11 are connected to amplifiers 12 and 13, respectively. amplifier
The output of 12 is connected to a filter 14 for 5 KHz ₂ , 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 the comparator 16 is connected to an amplifier 19
And the output is connected to the display device 20.

FIG. 5 is a diagram showing the outputs at points a and b indicated by crosses in FIG. 4 with the position of the measuring needle 3 in the root canal 2 taken along the horizontal axis. In the circuit configuration shown in FIG. 5, it is assumed that the fundamental frequency of the pulse generator 10 is set to 1 KHz. Now, the dentist slowly inserts the measuring needle 3 into the root canal 2. At this time, the pulse generator 10 multiplexes and outputs a 1 KHz impulse signal and a 5 KHz impulse signal at a predetermined cycle. A weak current in response to this output signal and the impedance between the measurement needle 3 and the one electrode 5
11, the weak current is amplified by amplifiers 12 and 13, respectively.

Of these, only those responding to the 1 KHz impulse signal pass through the filter 17 and the output at point a (FIG. 4) is as shown at a in FIG. Similarly, only the signal responding to the 5 KHz impulse signal passes through the filter 14 and the output at the point b (FIG. 4) is indicated by b in FIG.

That is, while the measuring needle 3 moves in the root canal 2, the impedance between the measuring needle 3 and the one electrode 5 is substantially constant, and the outputs at the points a and b in response to each frequency of the input signal are the fifth.
As shown by a range I in FIG. In this state, the impedance between the measurement needle 3 and the one electrode 5 decreases near the position where the measurement needle 3 goes out of the root canal 2. In response to this change in impedance, points a and b
Although the output at the point increases, the range II in FIG.
As shown in the figure, the output a changes slowly and the output b changes quickly.

Here, focusing on the difference between the two outputs a and b, the rate of change of the outputs a and b differs depending on the frequency characteristic for each input frequency. The point at which the difference between b and b is minimum is detected as the position of the apical hole 6.

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

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

In order to solve the above-mentioned problem, the present applicant first detects that the differential output has reached a specific value, thereby enabling the accurate detection of the peak hole position. A hole position detection device was proposed.

Referring again to FIG. 5, the operation principle of the apical hole position detecting device previously proposed by the present applicant will be described.
In the figure, a and b are, for example, 1 KHz and
This is an output signal at a frequency of 5 KHz. Here, a voltage a 'corresponding to a difference from b in the region I is applied to a as a bias value. Then, in the region I, the values of a and b become equal, and in the region II, a becomes a ″ and b
Becomes b ', and the difference between the two changes as the measuring needle 3 advances. Thus, the present applicant has found that the value of the difference between a ″ and b ′ at a position corresponding to the minimum value of the difference between a and b is substantially constant from clinical data regardless of individual differences. (The current value at the apical position is almost the same for all persons).

Thus, by adding (or subtracting) the difference in the region I to the output signal of one frequency as a bias value, the two values in the region I are made equal, and the output value of the circuit for detecting the difference is a predetermined constant value. It was found that it was possible to determine the position of the apical foramen at the point in time.

FIG. 6 shows a circuit below the comparator 16 in FIG. 4, in which 21 is an adder / subtractor (comparator 16), 22 is an amplifier, 23 is a display, 24 is a storage circuit, and 25 is Erase circuit, 26,2
7, 28 are pulse generators. An output signal at a frequency of 1 KHz is applied to a terminal a, and an output signal at a frequency of 5 KHz is applied to a terminal b. An output voltage of the difference is obtained by an adder / subtractor 21 and displayed on a display 23 via an amplifier 22. Memory circuit
Reference numeral 24 stores the output value of the amplifier 22 by the storage pulse from the pulse generator 26, and is reset by a signal from the erasing circuit 25. The pulse generator 27 generates an erase pulse for driving the erase circuit 25. When the reset switch 29 is pressed, the pulse generating circuits 26 and 27 are activated based on the reset pulse from the pulse generator 28. As shown in FIG. 7, the storage pulse is generated after the erase pulse. . The value stored in the storage circuit is applied to one input, for example, an input terminal a as a bias value.

FIG. 8 is a diagram for explaining the operation of FIG. 6, in which (I) shows a display unit and (II) shows an adder / subtractor unit.
(A) shows that at the start time, in this case, the stored value from the storage circuit 24 is 0, and when a voltage value of 2 is applied to the terminal a and a voltage value of 3 is applied to the terminal b, the output of the adder / subtractor 21 becomes 1 Becomes Here, when the reset button 29 is pressed, the storage circuit 24 is reset (in this case, there is no change because it is 0).
The difference 1 is stored. This is the state shown in FIG. 3B. In this case, 1 is added to the terminal a as a bias value.
The output of 21 is 0. When the measuring needle 3 is advanced, the area moves from the area I to the area II. When the difference becomes a constant value, here, a value of 5, it is understood that the position of the measuring needle 3 reaches the apical foramen (FIG. ). At the time of the next detection, the graph shown in (d) is used. However, if the condition of the root canal or the patient changes, the initial values do not always become the same as those shown in (a). That is,
(D) If the terminal a is 3 and the terminal b is 6, as shown in the figure, the output of the amplifier 22 becomes 2 because the storage circuit 24 stores 1. Here, when the reset button 29 is pressed,
By driving the erasing circuit 25 by the erasing pulse, the memory circuit 24 is first reset to 0 as shown in (e), and the output of the adder / subtractor 21 becomes 3. The storage circuit 24 is set to store the difference 3 by the storage pulse following the erase pulse. Therefore, as shown in FIG.
The bias value 3 is applied to the terminal e, and the position of the apical foramen can be detected when the display indicates 5 as shown in FIG.
In FIG. 8, for the sake of simplicity, the fixed value is set to 5, but the value of 5 has no meaning. In practice, a mark is attached to a position corresponding to the fixed value. When the meter needle comes to that position, it will be in the peak position.

As described above, according to the invention proposed earlier by the present applicant, the position of the apical foramen can be detected when the difference between the outputs based on the 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 when detecting the position of the apical foramen, the reset button must be pressed every time.
Workability was very bad.

An object of the present invention is to solve the above-mentioned drawbacks in the apical hole position detection device proposed by the present applicant, and to make the output of a and the output of b the same without pressing the reset button as described above. That is, an object of the present invention is to provide an apical hole position detecting device capable of automatically performing zero adjustment.

Configuration In order to achieve the above object, the present invention provides an apical hole position detecting device that detects an apical hole position based on an impedance change between a measurement needle and one electrode, and an oscillation that generates two kinds of different frequency signals. Circuit, a detection circuit for detecting the impedance change in response to each of the frequencies, a difference detection circuit for sequentially comparing each output of the detection circuit and outputting a difference, and an output of the difference detection circuit for calculating the difference. A feedback circuit that feeds back to one input of the detection circuit and adds (or subtracts) the output of the difference detection circuit to 0, an alarm unit that notifies that the output of the difference detection circuit has become 0, Display means for notifying that the output of the difference detection circuit has reached a predetermined value. Hereinafter, a description will be given based on examples of the present invention.

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 are comparators, 35, 36 are one-shot trigger (mono-multi) circuits, 37 is a flip-flop circuit, 38 is a pulse oscillator, 39 is a counter, 40 is a D / A converter, 41 is a timer, 42 is an alarm, and 43 is an indicator.

Figure 2 is a diagram showing the relative positional relationship between the measurement needle and root canal, in FIG, Z ₃ is located before the measuring needle is inserted into the root canal, Z ₂
The stylus is inserted into the root canal, the position range in which the 0 adjustment described later, the measurement Z ₁ is the finished 0 adjustments described above will be inserted towards the apex of the stylus from 0 adjust the position of the The range, Z _0, 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. Less than,
A description will be given based on an embodiment of the present invention with reference to FIG.

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

When the measuring needle 3 is inserted into the root canal 2 from this state, a voltage corresponding to the impedance in the root canal appears at the input terminals a and b of the difference detection circuit 31 according to the respective frequencies. As described above, the output voltage of the difference detection circuit 31 changes before and after the measurement needle 3 is inserted into the root canal 2.
This change in the difference voltage is detected by the first comparator 32 (FIG. 3, (b)), and the difference voltage is detected by the threshold value (T
One shot trigger (mono multi) when exceeding H ₁ )
The circuit 35 is activated (FIG. 3, (c)), the flip-flop circuit 37 is activated by its output signal (FIG. 3, (d)), and the pulse oscillator 38 is activated by its output (FIG. 3, (C)). e)) The output pulses of the pulse oscillator 38 are integrated by a counter 39 (FIG. 3, (f)), and the integrated output is converted into an analog quantity by a D / A converter 40 and fed back to one input terminal of a difference detection circuit 31. Then, addition (or subtraction) is performed so that the output voltage of the difference detection circuit 31 becomes zero. Difference detection circuit 31
When the output voltage becomes zero, the second comparator 33 operates (FIG. 3, (g)), the one-shot trigger (mono-multi) circuit 36 operates (FIG. 3, (h)), and the flip-flop circuit is activated. The flip-flop circuit 37 is inverted (FIG. 3, (d)), the pulse oscillator 38 is stopped (FIG. 3, (e)), the integration of the counter 39 is stopped, and the counter 39 holds the integrated value. (FIG. 3, (f)). The comparator 33 uses 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 (FIG. 3,
(I)), the alarm 42 is activated (FIG. 3, (j)),
Notifies that the adjustment has been completed. After confirming this alarm, if the measuring needle 3 is further inserted, the indicator 43 will display
The predetermined position displayed on the display unit gradually increases in accordance with the voltage difference generated between the input terminals a and b of the difference detection circuit 31.
V ₀ (AP) is reached (FIG. 3, (a)). This display position is a display position corresponding to the apical position, and the value V ₀ (A
P) is a value common to all people, regardless of individual differences. Therefore, when the pointer of the indicator reaches this position, it can be determined that the tip of the measuring needle 3 has reached the position of the apical hole (Z ₀ ). The insertion length L of the measuring needle 3 at this time
By measuring the length of the root canal, the root canal length can be known. Thereafter, when the measuring needle 3 is pulled out by the root canal 2, the output voltage of the difference detector 31 indicates the output voltage of the D / A converter 40, and the change of the input terminal b at that time (FIG. 3, FIG.
(K)) is detected by the comparator 34 in FIG. 3 (FIG. 3,
(L)), the counter 39 is reset by the output (FIG. 3, (f)) and returned to the initial state (FIG. 3, FIG.
(A)).

Effects As is apparent from the above description, according to the present invention, in detecting the position of the apical foramen, the measuring needle is simply inserted into the root canal, and for a while, that is, until the alarm sound is heard. If this state is maintained, zero adjustment is automatically performed during that time, so that a very easy-to-use root canal length measuring apparatus can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a main part for describing an embodiment of the present invention, FIG. 2 is a diagram showing a relative positional relationship between a measuring needle and a root canal, and FIG. 3 is a diagram showing an operation of the present invention. FIG. 4 is a configuration diagram for explaining an example of a conventional root canal length measuring device, FIG. 5 is a diagram for explaining the operation principle, and FIG. FIG. 7 is a structural diagram for explaining an example of a root canal length measuring device previously proposed by the applicant, and FIG.
FIG. 8 is a diagram showing a pulse signal for operating the storage circuit and the erasing circuit shown in FIG. 8, and FIG. 8 is a diagram for explaining the operation of the root canal length measuring device shown in FIG. DESCRIPTION OF SYMBOLS 1 ... Tooth, 2 ... Root canal, 3 ... Measuring needle, 4 ... Oral mucosa, 5 ...
One electrode, 6 ... Apical hole, 10 ... Pulse generator, 11 ... Resistance, 1
2,13… Amplifier, 14,17… Filter, 15… Rectifier circuit, 16…
Comparator, 19… Amplifier, 20… Display, 21… Adder / Subtractor, 22…
Amplifier, 23 display, 24 storage circuit, 25 erasure circuit, 2
6, 27, 28 ... pulse generator, 31 ... difference detection circuit, 32, 33, 34
… Comparator, 35, 36… One-shot trigger circuit, 3
7 flip-flop circuit, 38 pulse oscillator, 39 counter, 40 D / A converter, 41 timer, 42 alarm, 43 indicator.

Claims (3)

(57) [Claims] An apex hole position detecting device for detecting an apical hole position based on an impedance change between a measuring needle and one electrode, an oscillation circuit for generating two kinds of different frequency signals, A detection circuit for detecting the impedance change in response, a difference detection circuit for sequentially comparing each output of the detection circuit and outputting a difference, and feeding back an output of the difference detection circuit to one input of the difference detection circuit A feedback circuit that adds (or subtracts) the output of the difference detection circuit to zero, an alarm unit that notifies that the output of the difference detection circuit has become zero, and an output of the difference detection circuit that has a predetermined value. And a display means for indicating that the condition has been changed. 2. The output of the difference detection circuit is configured to activate the feedback circuit when the measuring needle is inserted into a root canal to set the output of the difference detection circuit to 0 to generate the alarm, The dental apical hole position detecting device according to claim 1, wherein the predetermined value is indicated when the measuring needle is inserted up to the apical hole position. 3. The feedback circuit has a pulse generator and a counter for adding an output pulse of the pulse generator. The integrated value of the counter is fed back to one input terminal of the difference detection circuit, 3. The dental apical hole position detecting device according to claim 1, wherein the oscillation of the pulse generator is stopped when the output of the detecting circuit becomes zero.