JPS5977849A - Dental arch shape measuring device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dental arch shape measuring device that measures the shape of a test subject's dental arch from outside the oral cavity using ultrasonic waves.

Taking X-ray images of the teeth and jaws in an expanded form for dental diagnosis is known as so-called X-ray tomography, which uses an X-ray generator and an X-ray film device. This is done by moving the Xls generator and the Xi film device according to the shape of the dental arch while keeping the connecting line always intersecting the dental arch at a constant angle (for example, at a right angle). For this reason, an orthopantomography method is generally known in which the shape of the dental arch is approximated by a compound curve of 3@ circular arcs, and the XfA generator and X-ray film device are moved along this approximated curve. In addition, a method of approximating the dental arch with an ellipse is also known (for example, see Japanese Patent Publication No. 47-36953).
. However, since there are subtle individual differences in the shape and size of dental arches, it is impossible to approximate all of these with a compound curve of circular arcs or an elliptic curve, and it is impossible to approximate all of these with a compound curve of circular arcs or an elliptic curve. There is a problem that image quality deteriorates due to defocusing.

For this purpose, attempts have been made to directly measure the subject's dental arch and control the X-ray imaging device according to the measurement results.For example, an occlusal plate is inserted into the subject's oral cavity, and the It has been proposed to measure the shape of the dental arch of an individual test subject using switching types of pressure contacts (see Japanese Patent Laid-Open No. 136500/1983). However, since the occlusal plate method uses an occlusal pressure sensor, the measurement results obtained are the shape of the dental arch on the occlusal surface of the tooth, and the dental arch on the gingival area that is clinically necessary is not. You can only get different things. Also! Inserting a plate with air contacts into the oral cavity is undesirable from a safety point of view due to the risk of electric shock, and furthermore, when used in combination with an X-ray imaging device, the shadow of the grate may be It is necessary to remove the plate after the measurement of the dental arch is completed, and there is also the problem that the position of the subject's oral cavity, which has been positioned at this time, may shift.

The present invention focuses on these points, and provides a dental arch that allows accurate, simple, and safe measurement of the dental arch at the gum region, and allows easy X-ray photography in the measured state without any problems. It was developed for the purpose of providing a shape measuring device, and includes an ultrasonic distance measuring sensor and a senna position detector that detects the amount of displacement of this ultrasonic distance measuring sensor, and serves as a reference position for measurement. The support member has a plurality of distance measuring parts attached in an arc-shaped arrangement, and the distance measured by each ultrasonic distance measuring sensor when the sensor is brought into contact with the outer surface of the subject's jaw. a calculation unit that calculates the shape of the dental arch by calculating the position of the tooth to be measured with respect to the support member at each measurement point from data indicating the distance to the tooth and data indicating the position of the sensor with respect to the support member at the time of measurement; It is characterized by having the following.

Now, consider the quadratic X-Y plane that is in contact with the maxillary and mandibular tooth rows, and define the middle of the left and right central incisors as (x, y) = (.

, 0) coordinates, with the Y axis in the left and right direction,
If the Y-axis is taken in the anteroposterior direction, the tomographic trajectory that matches the dental arch can be approximated by the following quartic equation, and the (X
, Y) Once the coordinates are determined, the coefficients a4~a! can be calculated.

7 = B-aX' + asX" + 13-yiX"
+ a, xX - (1) Based on this principle, the present invention provides a plurality of distance measuring parts on a support member with a known shape, and uses this support member as a reference. The position of the ultrasonic distance measurement sensor with respect to the support member and the distance from the ultrasonic distance measurement sensor to the dental arch are measured, and these data are processed by the calculation unit to obtain the coordinates of each measurement point, and the method described in (1) above is performed. By calculating each coefficient of the equation, the shape of the subject's dental arch is calculated. Therefore, according to the present invention, there is no need to insert something such as an occlusal grate into the oral cavity, which poses a risk of electrical leakage or an obstacle to Xs1 imaging, and instead places the distance measuring unit on the outside of the subject's jaw, that is, on the buccal surface. Since measurements can be made just by touching them, they can be easily and safely measured. By appropriately selecting the measurement points, the shape of the dental arch in the groin area can be measured. In combination with a controlled X-ray imaging device, the measurement results can be used as is to perform X-ray imaging without moving the oral cavity position.
It is possible to take line tomography photographs and the like.

Furthermore, in the present invention, a plurality of different dental arch models μ are stored in the storage device of the calculation unit, and the dental arch shape calculated from the measurement results is compared with each stored model to find the closest shape. It is also possible to adopt a configuration in which the dental arch model μ of By changing the number, it is possible to perform X-ray imaging of any cross section corresponding to the measured dental arch shape.

The X-ray imaging device combined with the device of the present invention is provided with an X-ray generator and an X-ray film device facing each other on both sides of a rotatable arm, and the arm is arranged on the nine X-Y plane. A device configured to move along the same line, for example, the device described in Japanese Patent Publication No. 1053/1983 filed by the present applicant, is used.

Next, an embodiment in which the present invention is combined with the above-mentioned X-ray imaging apparatus will be described with reference to the drawings.

FIG. 1 is a plan view along a plane including the dental arch of a patient with a distance measuring unit in contact with the jaw of the subject.

In the figure, (1) is the subject's dental arch, (2) is the buccal surface, (
3) is a support member curved in an arc shape, and (7) is a support member (
3), and the distance measuring section (7) is a direct-M sliding type potentiometer (4) which is a sensor position detector. Sonic distance measurement sensor? ′(5).

Fig. 2 shows an example of a specific configuration of the distance measuring part (7). bar θ
Cut a thread on the tip of the tip and attach the ultrasonic distance measurement sensor (5), θ■ is the output lead of the potentiometer (4), and (6) connect the ultrasonic distance measurement sensor (5) to the buccal surface (
2) This is a spring that presses against the 6υ is the sensor housing, II is the sensor output lead wire, (E) is P
Piezoelectric element for generating ultrasonic waves such as ZT, piezoelectric element (b)
The front part of is glued to the inner surface of the metal case made of a thin plate using epoxy adhesive, etc., and the stain electrode is glued to the rear part using the same adhesive. The six metal cases and the electrodes are pulled out and the metal cases are welded to the sensor housing via a layer of vibration-absorbing adhesive such as silicone rubber adhesive.

6 is an impedance matching layer provided on the front surface of the metal case, which efficiently propagates the ultrasonic waves generated by the vibration of the piezoelectric element to the buccal or labial surfaces, and at the same time transmits the ultrasonic waves from the teeth to the lips. In order to efficiently receive the reflected ultrasound, the piezoelectric element has a characteristic impedance that is the geometric mean of the characteristic impedance of the piezoelectric element and the characteristic impedance of the human cheek, and the length in the ultrasound propagation direction is the same as that of the matching layer at the frequency used. It is configured to have a size that is 1/4 of the wavelength in (b). A specific material used is, for example, a plastic material such as epoxy resin mixed with a certain amount of rubber particles.

Figure 3 is a Glock diagram of an electric circuit that measures the distance between the sensor (5) and the dental arch (1) using an ultrasonic distance measuring sensor (5), and Figure 4 is a timing chart of the same circuit. It is.

In Fig. 3, (311) is an oscillator, and in Fig. 4 (
A signal with a constant frequency as shown in the diagram is continuously oscillated during measurement. (310) is a gate circuit that converts the output of the oscillator (311) into a constant cycle burst wave as shown in FIG. ) is driven by the output of the piezoelectric element 0, and transmits an ultrasonic signal as shown in FIG. 1g4) is received by the piezoelectric element r4.

The ultrasonic echo signal μ received by the piezoelectric element φ passes through a capacitor (301) and is sent to the first RF amplifier (302).
), and is amplified by the second RF amplifier (304) in the upper stage, which is adjusted to an appropriate level μ by a semi-fixed resistor (303), and a higher signal as shown in Fig. 4 (θ) is generated. The signal is input to the threshold detector (30). Here, the signal is subjected to full-wave detection as shown in Fig. 4 (0) and generates a detected voltage as shown in the envelope shown by the broken line, as shown in Fig. 4. (Figure 4 (2))
The output signal shown in is obtained.

(306) starts an integral operation at a constant voltage or constant current at the same time as the transmission of the burst wave shown in Fig. 4 m starts, and as shown in Fig. 4 (2)
The waveform shown in Figure 4 (C) is obtained using an integrating circuit that stops the integration operation at the rising edge of the output signal of A hold voltage as shown in Figure (1) is output.The value of this hold voltage is determined by the time from the start of transmitting the burst wave to the start of receiving the echo signal. The size is proportional to the distance Jl between the piezoelectric element and the tooth (more precisely, the reciprocating distance), assuming that it is constant in appearance, so this can be expressed as A/
A D converter (308) converts it into a digital signal that can be input to an arithmetic unit (401), which will be described later.

When transmitting the burst wave shown in FIG. 4(b), the control signal shown by the broken line in FIG. 4(to) is sent from the gate circuit (310) to the second RF amplifier (304). ) to prevent the receiver circuit from malfunctioning due to the transmitted burst wave during the period indicated by the broken line in FIG. 4). Further, the signal waveforms from a to 1 circuits of each company in FIG. 3 are indicated by the same symbols and circled in correspondence with FIGS. 4(a) to (1).

Next, FIGS. 5 and 6 will be explained. In FIG. 5, (401) ij: calculation section, (402) F! , a control spring μ that operates the calculation unit (401), and a control spring μ (403) that serves as a reference for operating the calculation unit (401).
(404) is the ultrasonic sensor section explained in FIGS. 1 to 4, and the output signal of the A/D converter (308) is input thereto. Further, (405) is an R/D that converts the output proportional to the resistance value of the potentiometer (4) shown in Figs. 1 and 2 into a digital signal that can be input to the calculation section (401).
In addition to the converter, each data obtained by the ultrasonic distance measurement sensors (5) and potentiometers (4) of the four distance measurement units (7) is input to the calculation unit (401).

(407) is the film cassette limit switch, (
4 (J8) it: Use the limit switch on the arm,
This is for forcibly stopping the operation if the operation exceeds the specified range. (411) is a stepping motor that moves the arm rotation axis in the X direction;
4) is a stepping motor that moves the arm rotation axis in the Y direction, (417) is a stepping motor that rotates the arm, and (420) is a stepping motor that drives the X-ray film cassette. ) (414) (417) (420)
are the drive circuits (410), (413), and (416), respectively.
) (419), each drive circuit (410) (413) (416) (419
) is a control circuit (40
9) Controlled by (412) (415) (418). (421) is a high-pressure generator, (422) is a filament drive unit, (423) is an X-ray tube, and a clock oscillator (403) constitutes these high-pressure generator (421) and filament drive unit (422). It also serves as a bus generator for the inverter.

In the above configuration, when a photographing preparation command is issued by the control spring /l/ (402), measurement result data is input from each distance measuring section (7) to the calculation section (401), and these data are processed. The shape of the dental arch is calculated.

Based on this, the optimal fault trajectory, tube voltage, and tube current are determined, and the high-voltage generator (421) is set to the appropriate value for the tube voltage, and the fiftment drive unit (422) is set to the appropriate value for the tube current, and then the control When the shooting start button of the spring (402) is pressed, each stepping motor (411) (414) (417) (420) is activated, and the arm rotates along the calculated trajectory in the X-Y plane. It rotates while moving above, and X-ray photography is always performed while drawing the tomographic trajectory closest to the subject's dental arch (1).

A microcomputer can be used for the arithmetic unit (401), and has a configuration as shown in FIG. 6, for example. In other words, (501) is C! PU, (506)
is the address bus fin, (50υhiro data bus fin,
(508) is a control path fin, and these path fins have ROM (502) and RAM as memory.
(503) is connected, and also a counter circuit (50
4) is connected. (505) is a parallel 110 circuit that receives commands from the control spring /l/ (402), data from the distance measuring section (7), and a limit switch (40
7) Input from (408), ROI~4 (502)
Output from 1 plant M (503) pha c, prJ (5og
The output of control signals, etc. based on the calculation results in Puffrel I
It is input and output via 10 circuits (505).

FIGS. 7 and 8 show other embodiments of the distance measuring section. In the figure, (to) is a piezoelectric film whose both ends are fixed to the support member (3) by fixed ports 1voe, and in Fig. 7, it is attached to the tip of the sliding rod (b) of the linear sliding type potentiometer (4). It shows a state in which the piezoelectric film (2) is pressed against the cheek surface (2) of the subject by the provided pressing part (2).

The pressure (on the film) is a film-like piezoelectric element such as PVDF or PVTF that generates a voltage (charge) proportional to the pressure. FIG. 8 shows its structure in an expanded state.

In the figure, (SOO) is the film-like piezoelectric element body, (
Reference numeral 801) denotes an electrode provided on the side of the suppressing portion (1) centering on the portion pressed against the cheek surface, and a pole (801) is formed on this ' by vapor deposition of aluminum, for example.

(802) is a lead wire, (803) is a thin electrically insulating layer made of polymer film such as vinyl chloride provided on the side that touches the cheek, (804) is a similar electrode, and (805) is ? [Pole (s
This is a protective layer made of a polymer film on the ol) side. The electrical insulating layer (803) has an acoustic impedance equal to that of the piezoelectric element body (
The material is selected to have a value between the acoustic impedance of the piezoelectric film (SOO) and the acoustic impedance of the cheek surface, and the portions (four locations in this example) of the piezoelectric film that are pressed against the cheek are The width is much larger,
Although the pressure points are continuous in the form of a film, there is sufficient acoustic separation between the pressure points. The operation of the distance measuring section (7) in the embodiment with is basically the same as that in FIGS. 1 and 2,
It can be used in combination with the circuits shown in FIG. 3 and below.

As is clear from the description of the embodiments above, the present invention supports a plurality of distance measuring units each including an ultrasonic distance measuring sensor and a sensor position detector that detects the amount of displacement of the ultrasonic distance measuring sensor. It is installed on a member and measures the position of the dental arch relative to the supporting member, and the shape of the subject's dental arch is calculated by the calculation unit.The measurement is simple and safe, and the measurement results can be obtained without changing the position of the oral cavity. It is possible to take an X-ray tomographic photograph using this method, and it also has the advantage of being able to accurately measure the shape of the dental arch in the dental area, which is clinically necessary. be.

[Brief explanation of drawings]

The drawings all show embodiments of the present invention. Fig. 1 is a plan view of the distance measuring section in use, Fig. 2 is a partially cutaway side view of the distance measuring section, and Fig. 3 is a distance measuring section. FIG. 5 is a block diagram of the electrical circuit of the entire device, FIG. 6 is a block diagram of the calculation section, FIG. 7 is a plan view of another embodiment of the distance measurement section, and FIG. FIG. 8(G) is a front view and a plan view of the piezoelectric film of the same embodiment. (Explanation of symbols) (1)...dental arch, (2)--buccal surface, (3)...
Support member, (4)... Potentiometer (sensor position detector), (5)... Ultrasonic distance measurement sensor, (7
)...Distance measuring section, Φargon...Piezoelectric element, Ring...Piezoelectric film, (401)...Calculating section. Representative Patent Attorney ((j2:, S5) Hidehiko Shibeki Figure 7 Figure 8 (a) et al. 8 Figure 8 (b)

Claims (1)

[Claims] 1. Consisting of an ultrasonic distance measurement sensor and a sensor position detector that detects the amount of displacement of this ultrasonic distance measurement sensor, a plurality of sensors are installed in an arc-shaped arrangement on a support member that serves as a reference position for measurement. data indicating the distance to the tooth to be measured when the distance measurement unit and each ultrasonic distance measurement sensor are brought into contact with the outer surface of the subject's jaw, respectively, and the distance to the support member at the time of measurement. A dental arch shape measuring device comprising: a calculation section that calculates the shape of the dental arch by calculating the position of the tooth to be measured with respect to the support member at each measurement point from data indicating the position of the sensor.