JPH0123449Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a device for measuring the thickness of tooth dentin using ultrasonic waves.

Generally, the inside of a tooth is composed of nerves and numerous tubes with an outer diameter of 1 to 2 microns that supply nutrients from the nerve parts.

Currently, when treating cavities, etc., a certain amount of enamel and dentin on the surface of the tooth is removed, and after appropriate treatment, a crown is placed over the tooth.

However, conventional treatment methods have the following problems.

In other words, when the tooth is viewed from the front, as shown in Figure 1, the distance 6 between the surface of the dentin 2 and the nerve 1 can be seen by X-ray photography, but when the tooth is viewed from the side, as shown in Figure 2, the distance 6 between the surface of the dentin 2 and the nerve 1 is visible. Since there was no way to measure the distance between the surface of nerve 2 and nerve 1, treatment was based on ``experience and intuition.'' Therefore, cutting may be necessary to reach the nerve, which can cause anxiety and discomfort to the patient.Also, if the nerve is exposed and a crown is placed over it for treatment, bacteria may invade from the exposed area in the future. However, there was a possibility that a phlegm formed inside the body, which could lead to a secondary illness. In order to prevent the patient from feeling uneasy, it is possible to remove the nerve, but since removing the nerve has the disadvantage of making the tooth more brittle, it has become increasingly important to treat the tooth without removing the nerve as much as possible. is required.

Therefore, in order to avoid cutting too much of the dentin and exposing the nerve, and to keep the thickness of the dentin constant, we need a device that uses ultrasound to measure the thickness of the dentin (the distance between the dentin surface and the nerve). is proposed. This will be explained below using figures.

Figure 1 is a front view of a tooth with a crown placed on it, Figure 2 is a side view of a tooth with a portion of dentin removed and a crown placed on it, and Figure 3 is a side view of a tooth before a crown is placed on the tooth. shows.

In the figure, 1 is the nerve, 2 is the dentin, and 3 is the crown used for treatment. 4 is the gum part, 5 is the enamel covering the surface of the dentin 2, and 6 is the distance from the dentin surface to the nerve (dentin thickness) when the tooth is viewed from the front.

When treating cavities, etc., dentists use a cutting tool to cut the enamel and then a certain amount of dentin. 6 could be easily detected by taking X-rays, but the 3rd
Regarding the distance 7 from the dentin to the nerve shown in the side view of the figure, it has not been possible to measure it until now because the teeth are lined up and it is not possible to take an X-ray image from the side.

FIG. 4 is a diagram illustrating an ultrasonic thickness measuring device for measuring the distance 7, which will be explained below with reference to the figures.

In the figure, 8 is a tooth portion, and 10 is a probe that faces the dentin of the tooth via a couplant 9 such as water (in some cases, the probe and couplant are integrated). an ultrasonic probe that is arranged at
A receiving circuit 13 amplifies the ultrasonic echo signal obtained by the probe 10, and a display 15 (for example, a cathode ray tube, liquid crystal display, or plasma display) for displaying the ultrasonic echo from the receiving circuit in an analog manner. etc.), 14 is a time axis section for creating a triangular wave with the signal from the synchronization section 11 and adding this to the time axis of the cathode ray tube. Reference numeral 16 denotes a thickness measuring section which receives the output of the synchronizing section 11 and generates a time corresponding to the tooth surface, the output of a delay circuit 25, an ultrasonic echo signal, a time measuring circuit 17 which measures the ultrasonic propagation time, and this ultrasonic wave. Pulse generation circuit 19 during propagation time
and a propagation distance measuring circuit 18 that measures the ultrasonic propagation distance by counting the pulses generated from the ultrasonic wave.

The thickness information of the dentin 2 obtained by the propagation distance measuring circuit 18 is displayed on the display 21 as the distance between the cut dentin and the nerve (that is, the thickness of the dentin).

In addition, in the comparison circuit 22 that performs a comparison calculation between the propagation distance value 20 obtained by the propagation distance measurement circuit 18 and the reference thickness value preset by the setting means 23, in the process of cutting the dentin, , an alarm output 24 (eg to a buzzer or lamp) is sent when the propagation distance value 20 becomes equal to or less than the reference thickness value.

Devices with the above-mentioned functions can also confirm ultrasonic echoes using a cathode ray tube during the dentin cutting process, making it possible to determine cracks, corrosion, etc. in the dentin to a certain extent, and to check the surface of the dentin. It is possible to maintain a constant distance from the nerve part.

Now, as shown in Figure 4, if one ultrasonic probe is used for both transmission and reception, depending on the shape of the tooth, it will propagate through the dentin, and the bottom surface of the nerve or dentin in the direction of ultrasound propagation. The drawback is that it is not possible to determine whether an echo obtained by the ultrasound probe is an echo from a nerve or not because the echoes from the ultrasound probe are not necessarily reflected back to the ultrasound probe and are scattered in other directions.

This idea was made to eliminate these drawbacks, and it uses two ultrasonic probes for transmitting and receiving,
Ultrasonic thickness measurement of teeth equipped with two amplification circuits that amplify each received signal from the two ultrasonic probes and a switching circuit that switches the output of the two amplification circuits. It provides equipment.

An embodiment of this invention shown in FIG. 5 will be described below. The tooth ultrasonic thickness measuring device of this invention consists of a synchronization section 11 that generates a synchronization signal, a transmission signal generation circuit 12 that generates a transmission signal, and a first ultrasonic probe 10 that serves both to generate and receive ultrasonic waves. dentin 2
A second ultrasonic probe 26 receives the ultrasonic waves transmitted by the first ultrasonic probe and amplifies the ultrasonic signals received by the first ultrasonic probe 10. A first reception amplification circuit 13, a second reception amplification circuit 27 that amplifies the ultrasonic signal received by the second ultrasonic probe 26, and an output of the second reception amplification circuit. A switch 30 that compares the level set by the level setter 29 with the comparator 28 and is controlled by the output of the comparator 28, and a thickness measuring unit 16 that measures the propagation time of the ultrasonic signal and converts it to the thickness of the dentin. , and a display 15 that displays the output of the thickness measuring section 16 and the output of the switching device 30.

Since the dental ultrasonic thickness measuring device of this invention is constructed as described above, the first ultrasonic probe 1
The ultrasonic signal generated at 0 has a reflection source on the dentin 2,
That is, if the nerve 1 is not present, the light will be transmitted to the second ultrasound probe 26. Further, if a nerve 1 exists in the dentin 2, the nerve 1 reflects the waves to the first ultrasonic probe 10.

The ultrasonic transmitted wave obtained by the second ultrasonic probe 26 is compared with the level set by the level setter 29 by the comparator 28, and if the level is higher than the level, the ultrasonic transmitted wave signal 32 is 30 and sent to the thickness measuring section 16 and display 15. Further, if the ultrasound transmitted wave is below the determination level, there is a nerve 1 in the dentin 2, and the wave is reflected by the nerve 1 without being transmitted to the second ultrasound probe 26. In this case, the comparator 28 causes the switch 30 to select the ultrasonic echo signal 31 of the dentin of the tooth, and sends it to the thickness measuring section and the display 15. The distance to the nerve 1 can be determined by the selected position of the switch 30.

Based on the above, this invention monitors the ultrasonic wave transmitted through the dentin 2 obtained by the second ultrasonic probe 26 and controls the switching device 30 to detect the nerves present in the dentin 2. 1 can be reliably measured.

[Brief explanation of the drawing]

Figure 1 is a front view of the tooth with a crown placed on it, Figure 2 is a side view of the tooth before the crown is placed on the tooth, Figure 3 is a side view of the tooth with the crown placed on it, and Figure 4 is a side view of the tooth with the crown placed on it. FIG. 5 is a diagram illustrating an ultrasonic thickness measuring device for measuring thickness, and is a diagram showing an embodiment of this invention, in which 1 is a nerve, 2 is a dentin, 8 is a tooth, and 9 is a couplant, 10 is a first ultrasonic probe, 11 is a synchronization part,
12 is a transmission signal generation circuit, 13 is a reception amplification circuit,
15 is a display, 16 is a thickness measuring section, 26 is a second ultrasonic probe, 27 is a transmitted wave amplification circuit, 28 is a comparator, 29 is a level setter, 30 is a switch, 31
32 is an ultrasonic echo signal of the dentin of the tooth, and 32 is an ultrasonic transmitted wave signal. In the drawings, the same or equivalent parts are designated by the same reference numerals.

Claims (1)

[Scope of utility model registration request] a transmitting circuit that generates a transmitted signal; a first ultrasonic probe that generates an ultrasonic signal based on the transmitted signal from the transmitting circuit and receives the reflected ultrasonic signal after the ultrasonic signal is generated; a second ultrasonic probe that receives an ultrasonic signal generated by the first ultrasonic probe and transmitted through the dentin of the tooth; and the first and second ultrasonic probes. a first receiving circuit and a second receiving circuit that amplify the received signals of the second receiving circuit, and a comparison circuit that compares the ultrasonic signal transmitted through the dentin of the tooth amplified by the second receiving circuit with a reference level; Selection means for selecting the outputs of the first and second receiving circuits based on the output of the comparison circuit;
a thickness measuring section and a display device, the outputs of the first and second receiving circuits are switched by the selecting means and applied to the thickness measuring section and the display device; Judging whether the ultrasonic signal generated by the probe is passing through the dentin of the tooth or is being reflected by a nerve interposed in between, based on the output of the above-mentioned display or comparison circuit. An ultrasonic tooth thickness measuring device characterized by: