JP7496071B2 - Dental cutting instruments - Google Patents

Description

The present invention relates to a dental cutting instrument, and more specifically, to a dental cutting instrument that can perform cutting by finger action and cutting by mechanical vibration.

In dental treatment, cutting tools for root canal formation, such as reamers and files, are widely used. Known types of cutting tools include manual cutting tools that use finger movements to perform cutting (e.g., Patent Document 1) and mechanical cutting tools that use vibrations from a vibration generating device to perform cutting (e.g., Patent Documents 2 and 3).

The root canal treatment instrument described in Patent Document 1 is a manual cutting instrument that includes a metal cutting needle with a blade for cutting tooth structure, and a resin handle that is approximately cylindrical and has a larger diameter than the cutting needle. The dentist holds the root canal treatment instrument by pinching the side of the handle with his or her fingers, and cuts and removes tooth structure by rotating or moving the cutting needle up and down to form a root canal.

A typical tooth is composed of a crown that erupts from the gums and one to four roots that extend from the crown towards the alveolar bone. The material that constitutes the root (tooth substance) is mainly dentin, within which a pulp cavity is formed that extends towards the tip of the root, and within which the dental pulp is located. For example, if tooth decay progresses and inflammation occurs in the dental pulp, treatment involves cutting and removing the pulp to form a root canal, and if necessary, cutting the surrounding dentin to enlarge the root canal and filling the root canal with a filling material. Cutting instruments are used to form and enlarge the root canal in this way.

The thickness, length, and shape of dental pulp vary, so dentists select a cutting tool suitable for the tooth to be treated from a wide range of cutting tools with different needle thicknesses, lengths, and cross-sectional shapes to form a root canal. Even during treatment of the same tooth, cutting tools must be changed to different ones depending on the progress of root canal formation, and cutting tools are changed frequently. Furthermore, dental pulp is often narrowed and curved, so in order to properly cut and remove the pulp and avoid cutting dentin unnecessarily, dentists must carefully form the root canal by relying on the sense of their fingertips, which requires a high level of skill.

Next, cutting tools for root canal formation that are attached to a vibration generating device are conventionally known (for example, Patent Document 2). The cutting tool in Patent Document 2 is a mechanical cutting tool that cuts and removes tooth substance by applying vibrations from a vibration generating device. A chuck for attaching the cutting tool is provided at the tip of the vibration generating device, and the cutting tool is attached in a replaceable manner.

By applying mechanical vibrations such as ultrasonic vibrations to the cutting tool, tooth substance can be cut and removed, and root canals can be formed or enlarged, without rotating or moving the cutting tool up and down. However, such cutting tools require a dedicated item to be attached to the vibration generating device, which creates the problem of higher costs compared to the widely used inexpensive hand cutting tools.

Therefore, vibration generators to which a hand cutting tool can be attached have been proposed in the past (for example, Patent Document 3). Patent Document 3 describes a vibration generator to which a commercially available reamer can be attached. A reamer is a hand cutting tool equipped with a metal cutting needle and a resin handle, and the tip end of the vibration generator is provided with a bifurcated clamping part for clamping and holding the handle, and a clamping ring for fixing the clamping part. As a result, a commercially available reamer can be attached to the tip end of the vibration generator, which can suppress cost increases compared to using a dedicated product.

Japanese Patent Application Laid-Open No. 10-309286 Japanese Utility Model Application Publication No. 01-155417 Japanese Utility Model Application Publication No. 61-031414

In conventional devices that apply mechanical vibrations to a cutting tool, it is necessary to attach the cutting tool to the tip of the vibration generator. However, since the cutting tool needs to be replaced depending on the progress of root canal formation, there is a problem that the task of replacing the cutting tool on the vibration generator occurs frequently and is cumbersome.

Furthermore, conventional cutting instruments are either hand-operated or mechanical, and no cutting instrument is known that can be used appropriately for both cutting by manual action and cutting by mechanical vibration during treatment.

The cutting tool in Patent Document 3 becomes a mechanical cutting tool when attached to a vibration generating device, and becomes a hand cutting tool when detached from the vibration generating device. Therefore, if one wishes to use both tools, treatment must be interrupted to attach and detach the tool. For this reason, compared to using both a hand cutting needle and a mechanical cutting needle, the need for attachment and detachment makes the tool more complicated.

For example, when forming a root canal using a hand cutting tool, the cutting needle may become locked, digging into the tooth structure and becoming immobile. In such a case, forcing the cutting tool to rotate will break the cutting needle. If mechanical vibrations can be temporarily applied to a hand cutting tool that has fallen into this locked state, it is possible to release the tool from the locked state without damaging the cutting needle. However, in the case of the cutting tool of Patent Document 3, it is difficult to attach it to a vibration generating device without removing it from the patient's mouth, and it is not possible to switch between cutting by manual action and cutting by mechanical vibration without interrupting treatment.

The present invention has been made in consideration of the above circumstances, and aims to provide a cutting instrument that can utilize both cutting by finger motion and cutting by mechanical vibration. It also aims to provide a cutting instrument that can selectively utilize cutting by finger motion or cutting by mechanical vibration. In particular, it aims to provide a cutting instrument that can switch between cutting by finger motion and cutting by mechanical vibration without removing it from the patient's oral cavity and interrupting treatment.

The dental cutting instrument according to the first aspect of the present invention is a dental cutting instrument comprising a metal cutting needle for cutting and removing tooth substance to form or enlarge a root canal, and a resin handle portion formed at one end of the cutting needle and having a diameter larger than that of the cutting needle, the handle portion comprising a side portion to be grasped with the fingers to rotate or move the cutting needle up and down, and an opening provided on the side opposite the cutting needle, and an engagement recess into which the tip of a vibration generating device is inserted during the formation of the root canal.

By adopting such a configuration, the side of the handle portion can be grasped with the fingers, and the tooth substance can be cut by manual movement, thereby forming or enlarging the root canal. In addition, by inserting the tip end of the vibration generator into the engagement recess provided at the rear end of the handle portion, the tooth substance can be cut by mechanical vibration, thereby forming or enlarging the root canal. Therefore, both cutting by manual movement and cutting by mechanical vibration can be used without removing the cutting tool from the patient's mouth. In addition, these can be used selectively. In particular, if the cutting tool falls into a locked state in which it cannot move during cutting by manual movement, it is possible to escape the locked state by temporarily applying mechanical vibration.

In addition to the above configuration, the dental cutting instrument according to the second aspect of the present invention is configured such that the inner wall of the engagement recess is tapered and the bottom area of the engagement recess is narrower than the opening area of the engagement recess.

By adopting this configuration, it is relatively easy to ensure a large contact area between the tip and the inner wall surface by simply inserting the tip of the vibration generating device into the engagement recess, compared to when the inner wall surface does not have a taper, and mechanical vibrations can be transmitted effectively.

In addition to the above configuration, the dental cutting instrument according to the third aspect of the present invention is configured so that the cutting needle is exposed from the inner wall surface of the engagement recess and can come into contact with the tip end.

By adopting such a configuration, the tip end of the vibration generator can be brought into direct contact with the cutting needle, and mechanical vibrations can be transmitted effectively. Furthermore, by exposing the cutting needle from the inner wall surface of the engagement recess, the tip end of the vibration generator can be easily brought into contact with the cutting needle simply by inserting the tip end of the vibration generator into the engagement recess.

In addition to the above configuration, the dental cutting instrument according to the fourth aspect of the present invention is configured such that the cutting needle does not cross the opening and its tip is positioned in the internal space of the engagement recess.

By adopting this configuration, the protruding part of the cutting needle does not protrude outside the engagement recess, and there is no need to worry about the protruding part of the cutting needle interfering with the cutting work performed by hand movements. It is also safe and there is no need to worry about accidentally injuring the inside of the patient's mouth.

In addition to the above configuration, the dental cutting instrument according to the fifth aspect of the present invention is configured such that the engagement recess has a metal engagement wall arranged along its inner wall surface, and the engagement wall is connected to the cutting needle.

By adopting this type of configuration, vibrations can be transmitted using only metal, allowing mechanical vibrations to be propagated effectively.

In addition to the above configuration, the dental cutting instrument according to the sixth aspect of the present invention is configured such that the engagement recess has a number of mating projections arranged in a circumferential direction, protruding inward from the inner peripheral surface, and the mating projections are capable of mating with the end of the flat cross section of the tip tip.

By adopting this configuration, the tip end of the vibration generator can be fitted into the fitting protrusion, and mechanical vibrations from the vibration generator can be effectively transmitted to the cutting needle.

In addition to the above configuration, the dental cutting instrument according to the seventh aspect of the present invention is configured such that the engaging protrusion has a rotational action surface that is inclined with respect to the radial direction and converts the insertion action of the tip end into a rotational moment, thereby generating a rotation of 1/8 of a turn or less.

By adopting this configuration, the dental cutting instrument can be rotated by inserting the tip end of the vibration generating device into the engagement recess. In addition, by rotating the instrument by less than 1/8 of a turn, it is possible to prevent the cutting needle from breaking.

According to the present invention, it is possible to provide a cutting instrument that can utilize both cutting by finger motion and cutting by mechanical vibration. It is also possible to provide a cutting instrument that can selectively utilize cutting by finger motion or cutting by mechanical vibration. In particular, it is possible to provide a cutting instrument that can switch between cutting by finger motion and cutting by mechanical vibration without removing it from the patient's oral cavity and interrupting treatment.

1 is an external view showing a configuration example of a dental cutting instrument 100 according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view of the dental cutting tool 100 of FIG. 1 cut along a plane including a central axis. 4 is an external view showing an example of a rear end surface of a handle portion 20. FIG. 1 is a diagram showing a state in which cutting is performed by hand using the dental cutting tool 100. FIG. 1 is a diagram showing a state in which cutting is performed by mechanical vibration using the dental cutting tool 100. FIG. FIG. 11 is an external view showing an example of a dental cutting instrument 101 according to a second embodiment of the present invention. 7 is a cross-sectional view showing a state in which a tip end 61 of a vibration generator is engaged with the dental cutting instrument 101 of FIG. 6. FIG. FIG. 11 is an external view showing an example of a dental cutting instrument 102 according to a third embodiment of the present invention. 7 is a cross-sectional view showing a state in which a tip end 61 of a vibration generator is engaged with the dental cutting instrument 101 of FIG. 6. FIG. FIG. 11 is a cross-sectional view showing another example of the dental cutting instrument 102 according to the third embodiment of the present invention, in which the tip end 61 of the vibration generator is engaged. 4 is an external view showing an example of a rear end surface of a handle portion 20. FIG. 2 is an enlarged view of a tip portion 61 of a tip 60 of a vibration generating device. FIG. FIG. 13 is a diagram showing an example of a dental cutting instrument 20 according to a fourth embodiment of the present invention. 13A and 13B are diagrams showing another example of a dental cutting instrument 20 according to the fourth embodiment of the present invention.

Embodiment 1.
Fig. 1 is an external view showing one configuration example of a dental cutting tool 100 according to a first embodiment of the present invention. Fig. 2 is a cross-sectional view of the dental cutting tool 100 of Fig. 1 cut along a plane including a central axis. The dental cutting tool 100 is a dental cutting tool used to cut and remove dental pulp where inflammation or the like is occurring to form a root canal, and includes a cutting needle 10 for cutting tooth substance, a handle portion 20 for grasping with fingers, and a stopper 30.

The dental cutting tool 100 can be used as a manual cutting tool that cuts tooth structure by finger movements. Manual cutting tools are classified into reamers, K-files, H-files, etc., depending on the cross-sectional shape of the cutting needle 10. For example, a reamer has a triangular cross-section and is used for cutting by rotating (reaming). An H-file has a circular cross-section with protrusions, has sawtooth projections in the axial direction, and is used for cutting by moving up and down in the axial direction (filing). A K-file has a square cross-section and is used for cutting by turning it 1/8 (45°) and pulling it up (turn and pull). The dental cutting tool 100 may be any of a reamer, K-file, H-file, etc.

The cutting needle 10 is a thin and long metal needle that gradually becomes smaller in diameter or cross-sectional area toward the tip. The cutting needle 10 is made of a metal material that can elastically deform to follow the curved shape of the root canal and is rust-resistant, such as stainless steel or nickel titanium (NiTi).

The cutting needle 10 is divided into a cutting area 11 at the tip and a non-cutting area 12 at the rear. The cutting area 11 is an area equipped with a cutting blade for cutting tooth substance to form and expand a root canal, and the non-cutting area 12 is an area not equipped with a cutting blade. The handle portion 20 and the stopper 30 are provided in the non-cutting area 12.

The handle portion 20 is a resin member that is grasped with the fingers to hold the dental cutting tool 100 during root canal formation, and is generally cylindrical in shape with a larger diameter (cross-sectional area) than the cutting needle 10, and is formed near the rear end of the cutting needle 10 so as to be generally coaxial with the cutting needle 10. The dentist holds the side of the handle portion 20 between his index finger and thumb, pinching it, and rotates or moves the dental cutting tool 100 up and down to form the root canal.

At the rear end of the handle portion 20, an engagement recess 21 is provided for inserting the tip of a vibration generating device (not shown). The engagement recess 21 is a recess formed at the rear end of the handle portion 20 toward the inside in the axial direction (the tip side). The shape of the internal space of the engagement recess 21 is arbitrary, but it is preferable that it has a shape that becomes smaller in diameter (cross-sectional area decreases) toward the bottom, such as a mortar shape. The rear end of the cutting needle 10 does not reach the engagement recess 21, but is arranged so as to be embedded in the handle portion 20. It is preferable that the side surface of the handle portion 20 is formed with multiple projections and recesses, or that both ends in the axial direction are larger in diameter than the center portion, making it less slippery.

The stopper 30 is a member for restricting the insertion length of the cutting needle 10, and is provided at a position a predetermined distance from the tip of the cutting needle 10. The stopper 30 is a disk shape with a larger diameter than the cutting needle 10, and is attached coaxially to the cutting needle 10. The stopper 30 abuts against the crown of the tooth, thereby preventing the cutting needle 10 from being inserted excessively.

Figure 3 is an external view showing an example of the rear end surface of the handle portion 20, and (a) to (c) in the figure show examples of the opening 22 of the engagement recess 21. The type of cutting needle 10 is indicated by the shape of the opening 22. (a) to (c) in the figure show examples of a reamer, a K-file, and an H-file. (a) shows a triangular opening 22 at the rear end of the handle portion 20, indicating that it is a reamer. (b) shows a circular opening 22 at the rear end of the handle portion 20, indicating that it is a K-file. (c) shows a square opening 22 at the rear end of the handle portion 20, indicating that it is an H-file. In all cases (a) to (c), the internal space of the engagement recess 21 has a similar cross section intersecting the axial direction and is a cone shape whose cross-sectional area decreases from the opening 22 to the bottom.

Figure 4 shows the state when cutting is performed by manual finger movements using the dental cutting tool 100. The dentist holds the dental cutting tool 100 by pinching the handle portion 20 with his fingers, and forms a root canal by rotating or moving the cutting needle 10 up and down.

Typically, one to four roots 51 extend from the crown 50. The root 51 is mainly made of dentin, and the dental pulp is formed near the center of the cross section of the root 51. By removing the dental pulp, a tubular space called a root canal is formed in the dentin. Since the dental pulp tapers toward the tip, the surrounding dentin is also cut and removed as necessary to enlarge the root canal. In addition, it is not uncommon for root canals to be curved, and since their shapes vary, the dentist relies on the sense of touch of his or her fingers to operate the dental cutting tool 100 and form the root canal.

Figure 5 shows the state when cutting by mechanical vibration is performed using the dental cutting tool 100, and the tip 61 of the tip 60 of the vibration generator is temporarily engaged with the dental cutting tool 100 and used as a mechanical cutting tool. If the dental cutting tool 100 becomes locked during root canal formation by manual action, the locked state can be safely released using mechanical vibration by temporarily engaging the vibration generator with the locked dental cutting tool 100.

During manual treatment, the dental cutting tool 100 may enter a locked state in which the cutting blade of the cutting needle 10 bites into the dentin and becomes immobile. If the dental cutting tool 100 is forcibly rotated in this state, the cutting needle 10 is likely to break due to metal fatigue. For example, the larger the diameter of the cutting needle 10, the less elastic it becomes. This is likely to occur when the dental cutting tool 100 is replaced while the root canal is being enlarged so that the cutting needle 10 is gradually increased in diameter from small to large. If a part of the cutting needle 10 remains in the root canal, it cannot be easily removed. The root canal is often curved at the apex, and if the dental cutting tool 100 is accidentally broken, it is extremely difficult to remove the broken part from the curved root canal, which may cause apical periodontitis.

When the tip end 61 of the vibration generator is inserted into the engagement recess 21 of the dental cutting tool 100 in the locked state, the mechanical vibration of the vibration generator can be transmitted to the cutting needle 10 via the handle portion 20. This allows the mechanical vibration to cut the tooth substance around the cutting needle 10, thereby releasing the locked state. At this time, the dental cutting tool 100 only needs to be held immovable, and the locked state can be released without damaging the cutting needle 10.

Even if the dental cutting tool 100 is not locked, mechanical vibrations from the vibration generator can be applied to the dental cutting tool 100 as necessary, if only temporarily. For example, when trying to enlarge a root canal in a place where the pulp is greatly curved, cutting by finger movement tends to cut the outside of the curved part more than the inside. Also, when the root is curved, rotating the cutting needle 10 may cause the cutting needle to twist, causing the cutting needle 10 to deviate from the original route, making it impossible to remove the pulp or infected dental tissue. Even in such a case, if the tip end 61 of the vibration generator is inserted into the engagement recess 21 and the cutting needle 10 is moved up and down while applying mechanical vibrations to the cutting needle 10, the outside and inside can be cut almost evenly, and it is possible to prevent the formation of a root canal that deviates from the original route.

The vibration generating device may be, for example, an ultrasonic generating device. Generally, an ultrasonic scaling device used for removing tartar is installed near the examination chair in a dental clinic, and can be used immediately during dental treatment. For this reason, it is convenient to use an ultrasonic scaling device as the vibration generating device of the present invention. The tip end 61 of the ultrasonic scaling device is sufficiently thin compared to the opening 22 of the engagement recess 21, and can be inserted into the engagement recess 21.

The inner wall surface of the engagement recess 21 is inclined so that the area of the opening 22 is larger than the bottom area. This makes it easier to increase the contact area with the tip end 61 of the vibration generator, allowing mechanical vibrations to be transmitted effectively.

Embodiment 2.
In the first embodiment, a dental cutting instrument 100 has been described in which the rear end of the cutting needle 10 is embedded in the handle portion 20 without reaching the engagement recess 21. In contrast, in the present embodiment, a dental cutting instrument 101 will be described in which the rear end of the cutting needle 100 protrudes into the engagement recess 21.

Figure 6 is an external view showing an example of a dental cutting instrument 101 according to embodiment 2 of the present invention. Also, Figure 7 is a cross-sectional view showing the state in which the tip end 61 of the vibration generating device is engaged with the dental cutting instrument 101 of Figure 6. Note that components corresponding to those shown in Figure 1 (embodiment 1) are given the same reference numerals and duplicated explanations are omitted.

The cutting needle 10 is positioned so that its rear end reaches the engagement recess 21 and protrudes from the inner wall surface of the engagement recess 21 into the internal space, and is exposed within the engagement recess 21. Therefore, the tip end 61 of the vibration generating device inserted into the engagement recess 21 can directly contact the cutting needle 10. Generally, metals have better vibration transmission characteristics than resins, so by directly contacting the tip end 61 with the cutting needle 10, mechanical vibrations can be efficiently transmitted to the cutting needle 10, and cutting of tooth substance can be performed more effectively.

The inner wall of the engagement recess 21 is inclined toward the opening, and the cross-sectional area of the internal space decreases from the opening toward the bottom. Therefore, by protruding the cutting needle 10 from the bottom of the engagement recess 21 and inserting the tip end 61 into the engagement recess 21, the tip end 61 can be easily brought into contact with the cutting needle 10.

Furthermore, the rear end of the cutting needle 10 does not intersect with the opening 22, but is positioned within the engagement recess 21. This does not reduce the efficiency of the cutting work performed by the fingers, as would be the case if the cutting needle 10 were to protrude from the handle portion 20, and also prevents accidental injury to the patient's oral cavity.

Embodiment 3.
In the second embodiment, a dental cutting instrument 101 was described in which the rear end of the cutting needle 10 protrudes into the engagement recess 21. In contrast, in the present embodiment, a dental cutting instrument 102 in which a metal engagement wall 23 is provided along the inner wall of the engagement recess 21 will be described.

Figure 8 is an external view showing an example of a dental cutting instrument 102 according to embodiment 3 of the present invention. Also, Figure 9 is a cross-sectional view showing the state in which the tip end 61 of the vibration generating device is engaged with the dental cutting instrument 102 of Figure 8. Note that components corresponding to those shown in Figure 1 (embodiment 1) are given the same reference numerals and duplicated explanations are omitted.

A metallic engagement wall 23 is provided on the inner wall surface of the engagement recess 21. The engagement wall 23 may be formed on the entire inner wall surface of the engagement recess 21, or may be formed on only a part of it. The illustrated engagement wall 23 has a cup shape and is arranged so as to cover the entire inner wall surface, including the bottom and side surfaces.

One end of the cutting needle 10 is connected to the engagement wall 23. The cutting needle 10 and the engagement wall 23 can be joined by any method that can transmit mechanical vibrations well, such as welding, screwing, fitting, or other methods.

The tip end 61 of the vibration generating device inserted into the engagement recess 21 can directly contact the engagement wall 23. Therefore, the mechanical vibration of the vibration wave generating device is transmitted to the cutting needle 10 via the engagement wall 23. Therefore, the mechanical vibration can be efficiently transmitted to the cutting needle 10, and the cutting of the tooth substance can be performed more effectively.

Figure 10 is a cross-sectional view showing another example of a dental cutting instrument 102 according to embodiment 3 of the present invention, showing the state in which the tip end 61 of the vibration generating device is engaged. Note that components corresponding to those shown in Figure 1 (embodiment 1) are given the same reference numerals and duplicated explanations are omitted.

In this dental cutting instrument 102, an engagement recess 21 is formed at the rear end of the cutting needle 10, and an engagement wall 23 is formed integrally with the cutting needle 10 as part of the cutting needle 10. The rear end of the cutting needle 10 is positioned so as to substantially coincide with the rear end of the handle portion 20, and the engagement recess 21 is formed on the rear end surface of the cutting needle 10 exposed from the handle portion 20.

As a result, the tip end 61 of the vibration generating device inserted into the engagement recess 21 can come into direct contact with the cutting needle 10, and the mechanical vibrations of the vibration wave generating device are directly transmitted to the cutting needle 10. As a result, the mechanical vibrations can be efficiently transmitted to the cutting needle 10, and cutting of the tooth substance can be performed more effectively.

Figure 11 is an external view showing an example of the rear end surface of the handle portion 20, and (a) to (c) in the figure show examples of the opening 22 of the engagement recess 21. The type of cutting needle 10 is indicated by the shape of the opening 22. (a) to (c) in the figure show examples of a reamer, a K-file, and an H-file. (a) shows a triangular opening 22 at the rear end of the handle portion 20, indicating that it is a reamer. (b) shows a circular opening 22 at the rear end of the handle portion 20, indicating that it is a K-file. (c) shows a square opening 22 at the rear end of the handle portion 20, indicating that it is an H-file.

Embodiment 4.
In the above embodiment, the cross section of the engagement recess 21 is a simple geometric shape such as a triangle, a rectangle, a circle, etc., and the inner peripheral surface is a smooth flat surface or a curved surface. In contrast, in the present embodiment, a case is described in which a large number of fitting protrusions 25 are provided on the inner wall surface of the engagement recess 21.

The tip end 61 of the scaling device can have a variety of shapes, but the cross section of the tip is relatively often flat. By making the inner wall surface of the engagement recess 21 shaped to fit with the tip end 61 having such a flat cross section, the vibration of the vibration generating device can be effectively transmitted to the cutting needle 10.

Figure 12 is an enlarged view of the tip 61 of the tip 60 of the vibration generating device. The tip tip 61 has a flat cross section. For example, it has a substantially elliptical or rectangular flat cross section, and has a pointed shape in which the longitudinal width of the cross section becomes shorter as it approaches the tip.

Figure 13 shows an example of a dental cutting instrument according to embodiment 4 of the present invention, where (a) is an external view showing the rear end face of the handle portion 20, and (b) is a cross-sectional view taken along the A-A cutting line in (a). A large number of mating protrusions 25 are formed in the circumferential direction on the inner wall surface of the engagement recess 21. In addition, mating recesses 26 are formed between adjacent mating protrusions 25, and a large number of mating recesses 26 are formed in the circumferential direction on the inner wall surface of the engagement recess 21.

As shown in (a) of the figure, the fitting protrusion 25 is a metal protrusion that protrudes radially inward from the inner peripheral surface of the engagement recess 21 having a circular cross section, and is formed integrally with the engagement wall 23 as a part of the engagement wall 23. The fitting protrusion 25 has a substantially triangular shape in a plan view, and is an approximately isosceles triangle with one apex extending from the inner peripheral surface toward the central axis J. A space is formed between the fitting protrusions 25 that face each other across the central axis J, for inserting the tip end 61. Also, as shown in FIG. 14(b), the fitting protrusion 25 is formed as a linear portion that extends linearly in the axial direction along the inner peripheral surface. The radial height of the fitting protrusion 25 becomes shorter as it approaches the bottom of the engagement recess 21, and the interval between the fitting protrusions 25 that face each other across the central axis J becomes narrower as it approaches the bottom of the engagement recess 21.

The mating recess 26 is a space formed by a pair of adjacent mating protrusions 25, and extends radially outward, with the inner peripheral surface of the engagement recess 21 forming the bottom. The width of the mating recess 26 narrows as it approaches the radially outer bottom. The mating recess 26 is also formed as a linear groove that extends linearly in the axial direction along the inner peripheral surface. The radial depth of the mating protrusions 25 becomes shorter as it approaches the bottom of the engagement recess 21, and the distance between the mating recesses 26 that face each other across the central axis J becomes narrower as it approaches the bottom of the engagement recess 21.

When a tip end 61 having a flat cross section is inserted into such an engagement recess 21, both ends of the flat cross section in the longitudinal direction enter and engage with the opposing engagement recesses 26. In other words, each end of the flat cross section in the longitudinal direction is fitted so as to be sandwiched between a pair of engagement protrusions 25 forming one engagement recess 26. If the tip end 61 has a pointed shape with a flat cross section, the tip end 61 can be fitted with the engagement protrusion 25 simply by inserting the tip end 61 into the engagement recess 21 by a predetermined insertion length, and mechanical vibration can be effectively transmitted to the cutting needle 10. The insertion length differs depending on the cross-sectional shape of the tip end and the shape of the inner wall surface of the engagement recess 21, but the tip end 61 can be fitted with the engagement protrusion 25 simply by inserting it into the engagement recess 21 until it stops.

Figure 14 shows another example of a dental cutting instrument according to embodiment 4 of the present invention, where (a) is an external view showing the rear end surface of the handle portion 20, and (b) is a cross-sectional view taken along the B-B cutting line in (a).

The mating protrusion 25 in FIG. 13 is an isosceles triangle in plan view, whereas the mating protrusion 25' in FIG. 14 is a scalene triangle with two sides 25a, 25b of different lengths that sandwich the apex pointing radially inward when viewed in plan. Similar to the case in FIG. 13, mating recesses 26 are formed between adjacent mating protrusions 25, the mating protrusions 25 are linear portions extending toward the bottom of the engagement recess 21, and the mating recesses 26 are linear grooves extending toward the bottom of the engagement recess 21.

The long side 25a of the engagement protrusion 25 is longer than the short side 25b and has a larger angle with respect to the radial direction. Therefore, when the tip tip 61 is inserted into the engagement recess 21, there is a high probability that both ends of the longitudinal direction of the flat cross section will come into contact only with the long side 25a. Since the long side 25a has an angle with respect to the radial direction, it applies a rotational moment around the central axis J to the handle portion 20, causing the cutting needle 10 to rotate. In other words, the inclined surface corresponding to the long side 25a becomes a rotational action surface that converts the insertion operation of the tip tip 61 into the rotational operation of the dental cutting instrument. This rotation is stopped when the tip tip 61 comes into contact with the short side 25b. At this time, the tip tip 61 is sandwiched between the long side 25a and the short side 25b of the adjacent engagement protrusion 25, and engages with these engagement protrusions 25.

All of the numerous engaging protrusions 25 are formed to generate a rotational moment in the same direction. The engaging protrusions 25 are also shaped to rotate the dental cutting instrument in the forward direction when the tip end 61 is inserted. Forward rotation is the direction of rotation that allows effective cutting, is predetermined by the cross-sectional shape of the cutting needle 10, and is usually right-handed (clockwise) rotation.

However, because there is a risk of breakage if the dental cutting instrument is rotated in a locked state more than 1/8 of a turn, it is desirable that the rotation by the fitting protrusions 25 be 1/8 of a turn or less. For this reason, for example, by arranging eight or more fitting recesses 25 in the circumferential direction, it is possible to prevent rotation from exceeding 1/8 of a turn.

By adopting such an engagement recess 21, when the tip end 61 is inserted into the engagement recess 21 and the tip end 61 is engaged with the engagement protrusion 25, the cutting needle 10 can be rotated by 1/8 of a turn or less. This allows the dental cutting instrument to be unlocked without breaking the cutting needle 10. In addition, it can be used not only when the dental cutting instrument is in a locked state, but also when cutting by mechanical vibration is to be temporarily and supplementarily utilized during cutting work by manual finger movements.

In this embodiment, an example has been described in which the fitting protrusion 25 is provided on the inner wall surface of the dental cutting instrument 101 (embodiment 2) in which the engagement wall 23 is formed within the engagement recess 21, but the present invention is not limited to this case. For example, it can also be applied to the dental cutting device part 100 of embodiment 1. In other words, the fitting protrusion 25 can also be provided on the resin inner wall surface of the engagement recess 21 that does not have the engagement wall 23.

REFERENCE SIGNS LIST 10 Cutting needle 11 Cutting region 12 Non-cutting region 20 Handle portion 21 Engagement recess 22 Opening 23 Engagement wall 25 Fitting protrusion 26 Fitting depression 30 Stopper 50 Crown 51 Root 60 Tip 61 Tip tip 100 to 102 Dental cutting instrument

Claims (7)

A dental cutting instrument comprising: a metal cutting needle for forming or enlarging a root canal by cutting and removing tooth substance; and a resin handle portion formed at one end of the cutting needle and having a diameter larger than that of the cutting needle.
The handle portion is
A side surface to be gripped by fingers in order to rotate or move the cutting needle up and down;
an end portion that is open on an opposite side to the cutting needle ;
The open end of the handle portion is provided with an engagement recess into which a tip end of a vibration generator can be inserted,
A dental cutting instrument, characterized in that the engagement recess has an opening and an internal space sufficiently large for the tip end. The dental cutting tool according to claim 1, characterized in that the inner wall of the engagement recess is tapered and the bottom area of the engagement recess is smaller than the opening area of the engagement recess. The dental cutting instrument according to claim 1 or 2, characterized in that the cutting needle is exposed from the inner wall surface of the engagement recess and can come into contact with the tip end. The dental cutting instrument according to claim 3, characterized in that the cutting needle does not intersect with the opening and its tip is positioned within the internal space of the engagement recess. The engagement recess includes a metal engagement wall disposed along an inner wall surface thereof,
4. The dental cutting instrument according to claim 1, wherein the engagement wall is connected to the cutting needle. The engagement recess has a number of fitting protrusions arranged in a circumferential direction and protruding inward from an inner circumferential surface thereof,
2. The dental cutting tool according to claim 1, wherein the fitting protrusion is capable of fitting with an end of the flat cross section of the tip end. The dental cutting instrument according to claim 6, characterized in that the engaging protrusion has a rotational action surface that is inclined radially and converts the insertion action of the tip end of the tip into a rotational moment, and when the tip end of the tip is inserted into the engagement recess and engages with the engaging protrusion, the dental cutting instrument rotates by less than 1/8 of a rotation around the central axis of the cutting needle .

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