JP7650772B2 - Dental Unit - Google Patents

Description

This disclosure relates to dental units.

A dental unit is a unit that is equipped with various pieces of equipment used during dental treatment, and is equipped with a patient chair in which the patient sits. The patient chair is constructed so that it can be raised and lowered, and the backrest can be tilted and stood up, to allow the patient to assume a position that is easy for treatment and procedures. The patient chair is also equipped with armrests that make it easy for the patient to get on and off the chair, and on which the patient can rest their arms when seated and grip when they become nervous during treatment.

Around the patient chair are a doctor's unit in which various tools used by the practitioner for dental treatment are arranged, an assistant hanger, a water supply unit for supplying mouthwash etc. to the patient, and an assistant unit in which a cuspidor for draining the water is arranged, and other items such as dental lights for illuminating the patient's mouth are also arranged as needed.

For example, when the patient's hand is placed on the housing of the assistant unit and the patient chair is lowered, if the patient's arm is positioned under the armrest, as shown in Figure 8, there is a risk that the arm will get caught in the armrest. Although such a situation is not anticipated very often, it is necessary to anticipate such a situation because children or people with disabilities may make unexpected movements during treatment, and even adults may adopt unexpected postures due to the special circumstances of treatment.

Patent document 1 discloses that the range in which the safety device is activated is changed depending on the volume voltage value for the height and inclination of the dental chair, and the safety device is activated when the height and inclination exceed a specified absolute value.

JP 2020-018465 A

However, conventional technology could not always detect problems such as those shown in Figure 8.

Therefore, in consideration of the above problems, the present disclosure aims to provide a dental unit that can increase safety in terms of preventing pinching in the armrest.

One aspect of the present disclosure is a dental unit comprising: a patient chair with a seat that can be raised and lowered and armrests that rise and fall following the seat; an assistant unit that is placed on the opposite side of the seat across the armrest; a pressure detection sensor that is provided on the assistant unit and detects pressure applied to the top surface of the assistant unit; and a calculation means that detects pinching by the armrest based on a signal from the pressure detection sensor.

The calculation means may be configured to detect pinching by the armrest based on the displacement of the seating portion per unit time and the change in pressure detected by the pressure detection sensor per unit time.

The dental unit disclosed herein can improve the safety of the dental unit in terms of preventing it from being pinched by the armrest.

FIG. 1 is a plan view of a dental unit 1 . FIG. 2 is a front view of the dental unit 1. FIG. FIG. 3 is a front view of the dental unit 1. FIG. FIG. 4 is a diagram illustrating the pinch calculation means 40. As shown in FIG. FIG. 5 is a diagram for explaining a case where an arm is caught in the armrest 3f. FIG. 6 is a diagram showing the calculation of pinch and the flow of control of the dental unit 1 based on the calculation. FIG. 7 is a diagram illustrating an example of detection by a sensor in (a) to (d). FIG. 8 is a diagram illustrating a manner in which an arm is caught in a conventional armrest.

1. Configuration of the dental unit Figures 1 to 3 show the appearance of a dental unit 1 according to one embodiment. Figure 1 is a plan view (viewed from above), and Figures 2 and 3 are front views (viewed from the direction of arrow II in Figure 1). The height position of the patient chair 3 differs between Figures 2 and 3, and in Figure 3 the patient chair 3 has been moved to a lower position than in Figure 2.
The dental unit 1 includes a base 2, a patient chair 3, a doctor unit 10, an assistant unit 20, a pressure detection sensor 30, and a pinching calculation means 40. In addition, a dental light (not shown) may be provided. The dental light may be of a known type.

1.1. Base The base 2 is disposed below the patient chair 3 and serves as the base of the patient chair 3. The base 2 has an outer shell formed by a housing, and various control devices are housed inside the housing. Examples of the control devices included here include a hydraulic circuit for raising and lowering, tilting and standing up the patient chair 3, and a hydraulic control means for controlling the hydraulic circuit. Therefore, a foot switch (not shown) is provided on the back side of the patient chair 3 of the base 2. The practitioner can operate the foot switch or an operation switch on the operation panel 11c of the doctor unit 10 to issue a command to the hydraulic control means and raise and lower the patient chair 3 and tilt and stand it up by controlling the hydraulic circuit.

1.2 Patient Chair In this embodiment, the patient chair 3 includes a seat 3a, a backrest 3b, a headrest 3c, a legrest 3d, a footrest 3e, and an armrest 3f.

The seat 3a is attached above the base 2 so that it can be raised and lowered. The seat 3a is raised and lowered by the hydraulic circuit housed in the base 2 as described above. Specifically, the practitioner operates the foot switch or the operation panel 11c of the doctor unit 10 described later, and the hydraulic control means receives the operation command and appropriately operates the hydraulic cylinders built into the hydraulic circuit, thereby raising and lowering the seat 3a. The backrest 3b, headrest 3c, legrest 3d, footrest 3e, and armrest 3f rise and lower together with the seat 3a. In other words, it can be lowered from the position shown in Figure 2 as shown in Figure 3, and conversely, it can be raised from the position shown in Figure 3 as shown in Figure 2.

The backrest 3b is a member that is rotatable around one end of the seating portion 3a, and supports the patient's torso. The backrest 3b can be tilted and raised so that the patient can sit or lie on his back. The backrest 3b is tilted and raised by a hydraulic circuit connected from within the base 2. Specifically, the practitioner operates a foot switch or the operation panel 11c of the doctor unit 10, and the hydraulic control means that receives the operation command appropriately operates a hydraulic cylinder built into the hydraulic circuit, causing the backrest 3b to tilt and stand up.

The headrest 3c is a member that is placed at the end of the backrest 3b opposite the end where the seating portion 3a is placed, and is a member that supports the patient's head. The headrest 3c is formed to be movable and rotatable so that the patient's head can be positioned in a position convenient for treatment. Such movement of the headrest 3c is performed by a mechanism including a motor built into the backrest 3b. Specifically, the practitioner operates a switch (not shown) provided on the back side of the backrest 3b or the headrest 3c, or an operation panel 11c of the doctor unit 10 (described later), and the headrest 3c moves and rotates when the mechanism receives the operation command and starts to operate.

The leg rest 3d is a member that is rotatable around the end of the seating section 3a opposite the side where the backrest 3b is placed, and supports the patient's legs. The leg rest 3d is rotatable so that it can assume a vertical or horizontal position in accordance with the tilted and standing position of the backrest 3b. Such rotation of the leg rest 3d is performed by a link mechanism that operates in conjunction with the tilting and standing of the backrest 3b. Specifically, when the practitioner operates the foot switch or the operation panel 11c of the doctor unit 10 as described above, the backrest 3b tilts and stands up, and the leg rest 3d rotates in conjunction with this.

The footrest 3e is a member provided in a direction extending from the legrest 3d, and is intended to support the patient's feet. Specifically, when the backrest 3b is in an upright position, i.e., a seated position, the footrest 3e is bent relative to the legrest 3d so as to receive the soles of the patient's feet. On the other hand, when the backrest 3b is reclined and the patient is lying on his back, the footrest 3e becomes roughly flat relative to the legrest 3d so as to receive the patient's heels. Means for moving the footrest 3e in this manner can be hydraulics, a motor, a link mechanism, etc., but are not particularly limited thereto.

The armrests 3f are arranged on either side of the seating section 3a in the width direction (the left and right direction of the patient when seated), and are positioned above the seating section 3a, with one end facing the backrest 3b and the other end being rod-shaped and extending away from the backrest 3b.

The patient chair 3 is provided with a sensor (posture sensor) that detects the posture of the patient chair 3. The posture of the patient chair includes the height position of the seat 3a, the reclining state (angle, etc.) of the backrest 3b, and the positions (angles, etc.) of the leg rest 3d and foot rest 3e. The sensor for detecting these postures is not particularly limited, but examples include a potentiometer, a slide volume, etc.

1.3 Doctor Unit The doctor unit 10 is provided on the side of the patient chair 3 opposite to the assistant unit 20, and in this embodiment has a work table 11, a first arm 12, and a second arm 13.
The work table 11 is a portion where various tools and switches required by the practitioner are provided. Specifically, the work table 11 has a work surface 11a on its upper surface, and a holder 11b is provided for storing handpieces used by the practitioner during treatment. Although not shown, the holder 11b holds various handpieces. Examples of handpieces include air turbines, micromotors, scalers, and syringes. Almost all handpieces are connected to electric circuits, water circuits, air circuits, and the like through tubes. In addition, an operation panel 11c is provided between the work surface 11a and the holder 11b. The operation panel 11c is provided with various operation switches, for example, for tilting and standing the patient chair 3, lifting and lowering operations, and switching on and off the dental lighting.
In this way, the holder 11b and the operation panel 11c are located on the back side of the patient chair 3 on the work table 11. This provides convenience for the practitioner who performs treatment near the patient's head.

The first arm 12 is a hollow rod-shaped so-called arm member, one end of which is disposed under the base 2 and is rotatable about an axis extending in the vertical direction. Therefore, the first arm 12 can rotate as shown by the arrow Ia in FIG.
The second arm 13 is also a hollow rod-shaped arm member. One end of the second arm 13 is disposed at the other end of the first arm 12, which is the end opposite the base 2. In addition, the workbench 11 is disposed at the other end of the second arm 13. The second arm 13 is connected to the first arm 12 so as to be rotatable about an axis whose axis is in the vertical direction, and can rotate as shown by the arrow Ib in FIG. 1.
The workbench 11 is connected to the second arm 13 so as to be rotatable about an axis extending in the vertical direction, and can be rotated as shown by the arrow Ic in FIG.

The work table 11 can therefore move and assume a certain position within a range that combines the above-mentioned rotations of the first arm 12, the second arm 13, and the work table 11 itself, improving the convenience of the practitioner. The practitioner can then change the position and position of the work table 11 by grasping a handle or the like of the work table 11 and pushing or pulling it.

The assistant unit 20 is a unit provided on the side of the patient chair 3 opposite the side on which the doctor unit 10 is arranged, on the opposite side of the seating section 3a of the patient chair 3 across the armrest 3f, and includes an assistant hanger 21 and a water supply and drainage section 29.

[Assistant Hanger]
The assistant hanger 21 is a portion in which tools mainly used by an assistant are provided, and includes a hanger portion 22, a first arm 23, and a second arm 24.

The hanger section 22 is a holder that stores handpieces (not shown) that the practitioner uses during treatment. Examples of handpieces include a vacuum, a saliva ejector, a syringe, and the like. The vacuum and saliva ejector are connected to a vacuum unit (not shown) via a suction tube.

The first arm 23 is a hollow rod-shaped so-called arm member, one end of which is disposed in the housing 29a of the water supply and drainage means 29 and is rotatable about an axis extending in the vertical direction. Therefore, the first arm 23 can rotate as shown by the arrow Id in FIG.
The second arm 24 is also a hollow rod-shaped arm member. One end of the second arm 24 is disposed at the other end of the first arm 23, which is the opposite end to the housing 29a of the water supply and drainage unit 29. The hanger unit 22 is disposed at the other end of the second arm 24. The second arm 24 is connected to the first arm 23 so as to be rotatable about an axis whose axis is in the vertical direction, and can rotate as shown by the arrow Ie in FIG. 1.
The hanger portion 22 is connected to a second arm 24 so as to be rotatable about an axis extending in the vertical direction, and can be rotated as shown by the arrow If in FIG.

The hanger section 22 can therefore move and assume a certain position within a range that combines the above-mentioned rotations of the first arm 23, the second arm 24, and the hanger section 22 itself, improving the convenience of the practitioner. The practitioner can then change the position and position of the hanger section 22 by grasping a handle or the like of the hanger section 22 and pushing or pulling the hanger section 22.

[Water Supply and Drainage Section]
The water supply and drainage section 29 is a section for supplying and draining water so that the patient can gargle and clean the inside of the mouth during and after treatment, and a known configuration can be applied to this section.
For example, the water supply and drainage unit 29 has a housing 29a, inside which are housed pipes for water supply and drainage and a cleaning circuit for cleaning the pipes.
In addition, the water supply and drainage unit 29 in this embodiment includes a spitting receptacle 29b and a water supply part 29c on the top surface of the housing 29a, and water supplied from the water supply part 29c is poured into a cup so that a patient can gargle using the cup and spit the water into the spitting receptacle 29b. Therefore, the spitting receptacle 29b is bowl-shaped to spit out water in the mouth after gargling. Saliva and water discharged into the spitting receptacle 29b are discharged through a drain trap provided inside the housing 29a of the water supply and drainage unit 29. In addition, the spitting receptacle may be movable in consideration of the convenience of a patient's posture. In that case, the spitting receptacle 29b can be moved in front of the patient when the patient gargles.

1.5. Pressure detection sensor The dental unit 1 is provided with a pressure detection sensor 30. In this embodiment, the pressure detection sensor 30 is a sensor arranged so as to detect the force of the upper surface of the housing 29a of the assistant unit 20 being pressed by something placed on the upper surface of the housing 29a. As described later, it is assumed that the sensor detects that a part of the hand or arm of a patient seated on the patient chair 3 is placed on the upper surface of the housing 29a of the assistant unit 20. Therefore, it is preferable that the range detected by the pressure detection sensor 30 includes at least the side of the upper surface of the housing 29a where the patient chair 3 is placed. Further, the specific range cannot be limited because it varies depending on the length of the armrest 3f, the positional relationship between the patient chair 3 and the housing 29a, the shape of the housing 29a, etc., but it is preferable to include at least the range where the patient's hand can touch the upper surface of the housing 29a while the patient is seated on the patient chair 3. In addition, although there is no particular limitation, it is preferable that the pressure detection sensor 30 is arranged on the surface of the upper surface of the housing 29a or embedded in a position close to the upper surface in order to increase sensitivity.

The specific form of the pressure detection sensor 30 is not particularly limited as long as it can detect the force of an object placed on the top surface of the housing 29a pressing against the housing 29a, but an example of such a sensor is a pressure sensor.

1.6. Entrapment Calculation Means The entrapment calculation means 40 receives an electric signal (e.g., voltage) from the pressure detection sensor 30 to determine whether entrapment has occurred in the armrest 3f, and controls whether to stop or continue the raising and lowering and tilting and standing of the patient chair 3 according to the determination. The specific determination process will be described later. The configuration of the entrapment calculation means 40 is conceptually shown in FIG. 4.
As can be seen from FIG. 4, the collision calculation means 40 includes an operator 41 , a RAM 42 , a storage means 43 , a receiving means 44 , and an output means 45 .

The operator 41 is configured by a so-called CPU (central operator) and is connected to each of the above-mentioned components, and is a means capable of controlling them. The operator 41 also executes various programs stored in the storage means 43, which functions as a storage medium, and performs calculations based on these programs as a means for generating various data and selecting data.

RAM 42 is a component that functions as a working area for operator 41 and a storage means for temporary data. RAM 42 can be composed of SRAM, DRAM, flash memory, etc., and is similar to known RAM.

The storage means 43 is a component that functions as a storage medium in which programs and data that are the basis for various calculations are stored. The storage means 43 may also be capable of storing various intermediate and final results obtained by executing the programs.

In this embodiment, one of the programs stored in the storage means 43 includes a calculation that determines whether pinching has occurred in the armrest 3f based on a signal from the pressure detection sensor 30, and issues a command to stop raising and lowering and tilting and standing up of the patient chair 3 when it is determined that pinching has occurred. Each specific step of this program is composed of steps that correspond to each process of the calculation described below.

Such a calculation can be performed, for example, in the following manner.
When a patient is seated on the patient chair 3 and the patient chair 3 is lowered from the position shown in Fig. 2 to the position shown in Fig. 3, if the patient's hand is placed on the upper surface of the housing 29a and the arm is positioned under the armrest 3f as shown in Fig. 5, the arm will be pinched in the armrest 3f. In response to this, the pressure detection sensor 30 acquires a signal of the increasing pressure, and the pinch calculation means 40 judges the pinch.
This allows the deformation of the patient chair 3 to be stopped immediately when pinching occurs as shown in FIG.

The receiving means 44 is a component that has the function of appropriately incorporating information from the outside into the pinch calculation means 40, and is connected to at least the pressure detection sensor 30.

The output means 45 is a component that has the function of appropriately outputting information that should be output from among the obtained results to the outside, and in this embodiment is connected to the hydraulic control means. As a result, when the pinch calculation means 40 determines that pinch has occurred in the armrest 3f, it issues a command to the hydraulic control means to stop the movement and rotation of the patient chair 3.

2. Operation Flow Next, the operation of the pinch calculation means 40 to permit and restrict the lifting and lowering and tilting and standing up of the patient chair 3 will be described. The operation flow is shown in Figure 6. As can be seen from Figure 6, the calculation by the pinch calculation means 40 includes steps S11 to S17. Each step will be described below.

In step S11, a command (deformation command) is issued to raise or lower the patient chair 3 and tilt or stand up. Such commands to raise or lower the patient chair 3 and tilt or stand up are issued, for example, by the foot switch or the doctor unit 10 as described above.

In step S12, signals are obtained from each sensor at a predetermined time, and the change in the signal (i.e., the change in the physical quantity) at that predetermined time is calculated. More specifically, this step includes steps S12a, S12b, and S12c.

In step S12a, a signal related to the posture of the patient chair 3 is obtained. As described above, the patient chair 3 is provided with a sensor (posture sensor) that detects the posture of the patient chair 3, and a signal (e.g., voltage, etc.) is obtained from the posture sensor.
As described above, the posture of the patient chair 3 can be represented by the height position of the seating portion 3a, the reclining state (angle, etc.) of the backrest 3b, and the arrangement (angle, etc.) of the leg rest 3d and foot rest 3e, but in this embodiment, the acquired data includes at least a signal representing the height position of the seating portion 3a.

In step S12b, a signal is obtained from a pressure detection sensor 30 provided on the housing 29a of the assistant unit 20. As described above, the assistant unit 20 is provided with a pressure detection sensor 30 that detects the pressure on the top surface of the housing 29a, and a signal (e.g., voltage, etc.) is obtained from the pressure detection sensor 30. This makes it possible to obtain the pressure applied to the top surface of the housing 29a of the assistant unit 20.

Here, signal acquisition in steps S12a and S12b is performed multiple times at a predetermined interval within a predetermined time so that the amount of change in each step can be determined. The predetermined time and the predetermined interval are not particularly limited, but for example, by setting the predetermined time to 1 second and the predetermined interval to 0.1 seconds, signals are acquired at 10 points within the predetermined time, and this data is used to calculate the amount of change in the next step S12c.

In step S12c, the amount of change in the height position of the patient chair 3 is calculated based on the signal acquired in step S12a, and the amount of change in the pressing force applied to the top surface of the housing 29a of the assistant unit 20 is calculated based on the signal acquired in step S12b. Figure 7 shows an example of the specific changes and amounts of change that can be obtained. Each graph shown in (a) to (d) of Figure 7 has time (predetermined time Δt) on the horizontal axis and signal (voltage) on the vertical axis. In the graphs, the solid line represents the pressing force applied to the top surface of the housing 29a of the assistant unit 20 acquired in step S12b, with the larger the value, the larger the pressing force. In the graphs, the dashed line represents the height position of the patient chair 3 acquired in step S12a, with the larger the value, the higher the position.

7A, during a predetermined time (Δt), the pressure detection sensor detects an increase in pressure corresponding to ΔV _s1 and a downward movement of the patient chair 3 corresponding to ΔV _c1 . That is, in this example, within the predetermined time, the patient chair 3 moves downward and the pressure applied to the upper surface of the housing 29a of the assistant unit 29 increases.
7B, during a predetermined time (Δt), the pressure detection sensor detects no increase in the pressure (ΔV _s2 =0), and the patient chair 3 moves downward by an amount equivalent to ΔV _c2 . That is, in this example, the patient chair 3 moves downward, but there is no change in the pressure applied to the upper surface of the housing 29a of the assistant unit 29.
7C, during a predetermined time (Δt), the pressure detection sensor detects an increase in pressure equivalent to ΔV _s3 , but the patient chair 3 does not descend (ΔV _c3 =0). That is, in this example, the pressure applied to the upper surface of the housing 29a of the assistant unit 29 increases, but the patient chair 3 does not descend.
In the example shown in Fig. 7(d), during a predetermined time (Δt), the pressure detection sensor detects an increase in pressure equivalent to ΔV _s4 and a descent of the patient chair 3 equivalent to ΔV _c4 . However, ΔV _s4 > ΔV _s1 . That is, in this example, within a predetermined time, the patient chair 3 descents and the pressure applied to the upper surface of the housing 29a of the assistant unit 29 increases. However, the degree (slope) of this increase in pressure is larger than that in Fig. 7(a).

In step S13, it is determined whether or not there is a possibility of being pinched by the armrest based on the amount of change that occurred within the specified time obtained in step S12. The specific criteria for the determination are not particularly limited, as long as the determination is based on a signal from the posture sensor of the patient chair and a signal from a pressure detection sensor that detects the pressure state of the top surface of the housing of the assistant unit.

As a more specific example, it is determined that pinching by the armrest will occur when the relationship between the increase in the amount of pressure (ΔV _s ) of the pressure detection sensor during a specified time (Δt) and the amount of descent (ΔV _c ) of the patient chair 3 during the specified time (Δt) obtained in process S12 satisfies a specified relationship.

7, the determination is made based on a predetermined relationship between the rate of change (ΔVs/ _Δt ) of the increase in pressure of the pressure detection sensor per unit time (ΔVs) and the rate of change ( _ΔVc / _Δt ) of the amount of downward movement of the patient chair per unit time ( _ΔVc ). The predetermined range is determined in advance by testing or the like to determine whether pinching will occur or not.

In Fig. 7(a), the pressure detected by the pressure detection sensor 30 increases as the patient chair 3 descends from the position in Fig. 2 to the position in Fig. 3. This is because the arm is pinched by the armrest 3f as shown in Fig. 5, and the hand presses the pressure detection sensor 30 as the patient chair 3 descends, increasing the pressure. At this time, the relationship between _ΔVs1 /Δt and _ΔVc1 /Δt is within a predetermined range. Therefore, in this case, it is determined in step S13 that the arm is pinched by the armrest 3f, Yes is selected, and the process proceeds to step S14.

7B, the pressure detected by the pressure detection sensor 30 does not change as the patient chair 3 is lowered, and the arm is not pinched by the armrest 3f. At this time, the relationship between ΔV _s2 /Δt and ΔV _c2 /Δt is not within the predetermined range. Therefore, in this case, it is determined in step S13 that the arm is not pinched by the armrest 3f, No is selected, and the process proceeds to step S15.

In Fig. 7(c), the patient chair 3 is not lowered. Therefore, the arm is not pinched by the armrest 3f. At this time, the relationship between ΔV _s3 /Δt and ΔV _c3 /Δt is not included in the predetermined range. Therefore, in this case, it is determined in step S13 that the arm is not pinched by the armrest, No is selected, and the process proceeds to step S15.

In Fig. 7(d), the pressure detected by the pressure detection sensor 30 increases while the patient chair 3 is lowered. However, the rate of change of the pressure per unit time, ΔV _s4 /Δt, is larger than the rate of change due to pinching, ΔV _s1 /Δt, as shown in Fig. 7(a). An increase in the pressure in this case may be caused, for example, by an object being placed on the upper surface of the housing 29a of the assistant unit 20, causing a sudden increase in the pressure. Therefore, in this case as well, the arm is not pinched by the armrest 3f. In this case, the relationship between ΔV _s4 /Δt and ΔV _c4 /Δt is not included in the predetermined range. Therefore, in this case, it is determined in step S13 that the arm is not pinched by the armrest, No is selected, and the process proceeds to step S15.

In step S14, because it was determined in step S13 that there was a possibility of an arm being pinched by the armrest (for example, the example in FIG. 7(a)), the deformation of the patient chair 3 is stopped. This makes it possible to avoid problems caused by pinching.

In step S15, since it was determined in step S13 that the arm was not pinched by the armrest (e.g., Figures 7(b) to 7(d)), the deformation of the patient chair 3 continues.

In step S16, after the patient chair 3 has been raised and lowered and tilted and stood up (transformed) in step S15, it is determined whether the originally planned transformation has been completed.
If the originally planned transformation is completed, Yes is selected and the process proceeds to step S17, where the transformation of the patient chair 3 is completed.
On the other hand, if the originally planned raising/lowering and tilting/standing (deformation) of the patient chair 3 has not yet been completed, No is selected and the process returns to step S12.

As described above, the dental unit 1 equipped with the pressure detection sensor 30 and the pinch calculation means 40 can prevent the patient's arm from being pinched by the armrest 3 f when the patient places his/her hand on the upper surface of the housing 29 a of the assistant unit 20.

REFERENCE SIGNS LIST 1 dental unit 2 base 3 patient chair 3f armrest 10 doctor unit 20 assistant unit 29 water supply and drainage section 29a housing 30 pressure detection sensor 40 pinching calculation means

Claims (2)

A patient chair including a seat portion that can be raised and lowered and armrests that rise and fall following the seat portion;
An assistant unit disposed on the opposite side of the seat with the armrest in between;
A pressure detection sensor provided on the assistant unit for detecting a pressure applied to an upper surface of the assistant unit;
and a calculation means for detecting pinching by the armrest based on a signal from the pressure detection sensor.
Dental unit. The dental unit according to claim 1, wherein the calculation means detects pinching by the armrest based on the displacement of the seating portion per unit time and the change in pressure detected by the pressure detection sensor per unit time.

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