JP7370952B2 - dental files - Google Patents

Description

The present invention relates to a dental file used for forming and enlarging root canals in dental treatment.

As a dental root canal cutting tool, there are known files that cut the inside of the root canal by rotating or pushing and pulling in the axial direction. Files made of highly flexible nickel titanium are attracting attention.

Furthermore, from the perspective of speeding up treatment and reducing doctor fatigue, not only manual types but also electric engine files that are connected to handpieces are attracting attention.

A useful configuration for such a nickel titanium engine file is the dental file disclosed in Patent Document 1. The file in this document is composed of an arc-shaped land whose cross section is placed on a virtual circle and two floating vertices placed inside the virtual circle, and has a configuration that has high followability to the root canal shape. It has become.

However, although the configuration of Patent Document 1 is very useful in the finishing process of root canal formation, it has poor cutting ability in the pre-process of root canal treatment, which emphasizes the formation of prepared holes and the enlargement of the root canal. Run short.

In order to improve this cutting force, if the two floating vertices are arranged closer to the virtual circle side, the flexibility will decrease and the ability to follow the shape of the root canal will deteriorate, resulting in cutting in an unintended direction. Cause.

On the other hand, files that emphasize cutting force include an arc-shaped land whose cross section is arranged on a virtual circle and one circumscribed vertex located on the virtual circle, as in Patent Documents 2, 3, and 4. In this case, the cutting resistance is concentrated on one circumscribed vertex on the diagonal of the land, and problems such as locking and breakage due to digging during cutting become noticeable.

The concentration of cutting resistance becomes more pronounced as the blade angle becomes sharper, which is a factor that conflicts with the improvement of cutting force. As a method of dispersing the cutting resistance, a configuration using two vertices as in Patent Document 1 is also effective, but this configuration reduces flexibility as described above.

In addition, nickel titanium files are prone to breakage due to their material properties, and in the case of electric engine files, the load applied to the file due to engine drive increases, so patent documents 2, 3, and 4 With this configuration, safety issues remain as a nickel-titanium engine file.

International Publication No. 2019/198777 China Utility Model Publication No. 203724240 US Patent No. 5,713,736 US Patent No. 6,702,579

Therefore, an object of the present invention is to provide a dental file that is excellent in both cutting force and flexibility, has high safety during cutting, and is useful as a nickel-titanium engine file.

In order to solve the above-mentioned problem, the invention according to claim 1 provides a dental file including a spiral blade, wherein a cross section of the spiral blade includes a virtual circle constituting the outer shape of the spiral blade, and a virtual circle constituting the outer shape of the spiral blade. an arc-shaped land disposed above, and an acute-angled apex that is disposed protruding from the center of the virtual circle and constitutes the cutting edge of the spiral blade, and the acute-angled apex is on a diagonal line of the land. The floating vertex is arranged inside the virtual circle, and only one floating vertex is provided within the cross section.

In this way, by arranging acute-angled vertices on the diagonal of the land, the cutting force is increased, and by reducing the number of these vertices to one, the frequency of contact with the root canal wall is reduced compared to Patent Document 1, which has two vertices. Furthermore, by setting the floating apex to be set back from the inside of the virtual circle that constitutes the outer diameter envelope of the spiral blade, biting and breakage can be suitably avoided.

The reason why the floating apex is arranged diagonally to the land is to stably retreat the cutting edge while the arcuate land is in contact with the root canal wall.

The floating apex that retreats from this virtual circle actively works during root canal cutting to increase cutting efficiency, and when not cutting, such as when entering or pulling up a root canal, only the arc-shaped land comes into contact with the end of this arc-shaped land. By cutting only the obtuse angle part, it is possible to improve operability while suppressing excessive cutting.

Furthermore, even when pulling up when retraction occurs during cutting, the cutting edge formed by the floating apex is prevented from coming into contact with the root canal wall, making it easier to pull up.

On the other hand, in a configuration where there is no arcuate land in the cross section and the apex is simply offset, there is a risk that the formed root canal will be scraped if force is applied to the side during pulling up. In the configuration in which the floating apex is arranged, the land with low cutting force is guided along the root canal wall, so the floating apex remains in a retreated position and excessive cutting does not occur.

Here, the angle of the floating apex, that is, the blade angle, is preferably an acute angle from the viewpoint of improving the cutting force, and more preferably an acute angle of 50 degrees to 70 degrees from the viewpoint of ensuring strength such as ductility. Even with such a sharp apex, safety is ensured by retreating from the virtual circle, and by making the blade an acute angle of around 60 degrees, even ultra-fine files with a maximum outer diameter of 1 mm or less will not elongate. It is possible to ensure strength against breakage and breakage.

The above-mentioned cross section, which is a feature of the present invention, is preferably applied over the entire axial direction of the spiral blade, but it is sufficient if it is applied only partially, as long as the above-mentioned effect can be obtained. Alternatively, a hybrid spiral blade may be formed by combining a spiral blade to which the cross section according to the present invention is applied and a spiral blade having another cross section.

The invention according to claim 2 is the invention according to claim 1, in which when there is one land, the diagonal line is a straight line passing through a point on the land and the center of the virtual circle, and is two or more, the diagonal line is a straight line extending in a direction indicated by a composite vector of lines passing through one point on each land and the center of the virtual circle.

In this way, when there is only one land, by arranging the floating apex on a diagonal line passing from any point on the land to the center of the virtual circle, the floating apex is stabilized with the land touching the root canal wall. and retreat.

Also, if there are two or more lands, by placing the floating vertex on the composite vector from each land, it is possible to stably retreat one floating vertex even if there are multiple lands. can.

In the invention according to claim 3, in the invention according to claim 1, an offset amount by which the floating apex retreats inward from the virtual circle is 0.5% to 5% with respect to the diameter of the virtual circle. 2. The dental file according to claim 1, wherein the dental file is within the range of .

In this way, by optimizing the offset amount, both machinability and safety can be better achieved. That is, if the offset is too large, the cutting force will decrease and the cross-sectional area of the metal portion will become smaller, making torsional breakage more likely. On the other hand, if the offset is too small, problems such as digging will occur, so it is desirable to optimize the offset amount depending on the usage environment and the performance that is important. The above range is a useful range assuming a nickel titanium engine file.

Moreover, the invention according to claim 4 is characterized in that in the invention according to claim 1, the file is an engine file made of nickel titanium.

As described above, by applying the cross section of the present invention to an engine file made of nickel titanium, superiority in machinability and safety becomes more apparent.

According to the present invention, it is possible to provide a dental file that is excellent in both cutting force and flexibility, has high safety during cutting, and is useful as a nickel-titanium engine file.

1 is a side view and a sectional view showing the structure of a dental file according to a first embodiment of the present invention. FIG. FIG. 2 is a sectional view showing a modification of the cross section according to the first embodiment shown in FIG. 1; FIG. 3 is a cross-sectional view showing the structure of a dental file according to a second embodiment of the present invention. FIG. 3 is a cross-sectional view showing the structure of a dental file according to a third embodiment of the present invention. FIG. 7 is a cross-sectional view showing the structure of a dental file according to a fourth embodiment of the present invention.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a side view and a sectional view showing the structure of a dental file according to a first embodiment of the present invention. As shown in the side view of FIG. 5A, the file 10 of the first form is composed of a spiral blade 12, a transition part 14, and a shaft 16 from the tip side, and the spiral blade 12 provides a cutting function. It is coupled to the shaft 16 via the transition section 14 . These elements are integrally formed from nickel titanium wire through processes such as grinding, twisting, and heat treatment, and are connected to an electric handpiece (not shown) via a shaft 16.

FIG. 1(b) is an enlarged view of a portion indicated by a dotted line Ib in FIG. It has a twisted structure that appears in , and is formed as a tapered structure in which the virtual circle E, which is the envelope, becomes smaller toward the tip.

FIG. 1(c) is a vertical cross-sectional view taken from Ic-Ic in FIG. It is placed in a retreated position inside E.

FIG. 1(d) is a cross-sectional view taken from Id-Id in FIG. 1(b), and as shown in the figure, the land L is formed in an arc shape and overlaps with the circumference of the virtual circle E. placed in position. In addition, the floating vertex P is a position retreated inward from the virtual circle E by an offset amount x, and is on a diagonal line D passing through the center O of the virtual circle E from a point on the land L indicated by a black dot in the figure. will be placed in The floating vertex P has an acute angle configuration of 60 degrees.

Here, the offset amount x is defined as a ratio to the diameter d of the virtual circle E, and is set within the range of 0.5% to 5% with respect to this diameter d, and is the maximum offset considering the taper of the spiral blade. The diameter is set to 1 mm or less. In addition, it is desirable that the shape of the cross section be symmetrical about the diagonal line D, that is, line symmetrical, but as will be explained in the example below, it is not completely line symmetrical, and the floating apex P is centered on the virtual circle E. It is also possible to have an asymmetrical shape arranged to be shifted from the center line to the left and right.

FIG. 2 is a sectional view showing a modification of the cross section according to the first embodiment shown in FIG. 11A shows an example in which a diagonal line D is taken from a point on the left side indicated by a black dot on the land L, and FIG. 2B shows an example in which a diagonal line D is taken from a point on the right side. As shown in the figures, the cross section may have an asymmetrical shape in which the starting point of the diagonal line D is shifted left and right, and the floating apex P is shifted from the center. However, from the viewpoint of manufacturability and stability of the cutting edge, it is desirable that the cross section be symmetrical with respect to the diagonal line D as shown in FIG. 1(d).

FIG. 3 is a cross-sectional view showing the structure of a dental file according to a second embodiment of the present invention. The second form shown in the figure is an example in which the length of the land L is shorter than that of the first form and has a substantially diamond-shaped cross section.

As shown in this example, the diagonal line D that determines the position of the floating vertex P may be taken as the starting point at the left end of the land L as shown in (a) of the same figure, or as shown in (b) of the same figure. In this case, the center of the land L may be used as the starting point, or the right end of the land L may be used as the starting point, as shown in FIG. It is desirable to do so.

FIG. 4 is a cross-sectional view showing the structure of a dental file according to a third embodiment of the present invention. The third form shown in the figure is an example in which the length of the land L is shorter than the first form and longer than the second form.

As in Fig. 3, the starting points of the diagonal line D are the left end of the land L in (a), the center (b) in the figure, and the right end in Fig. 3 (c), as in Fig. 3. It can be selected as appropriate.

FIG. 5 is a cross-sectional view showing the structure of a dental file according to a fourth embodiment of the present invention. The fourth form shown in the figure is an example in which two arc-shaped lands, L1 and L2, are provided. When a plurality of lands are provided in this manner, diagonal lines D1 and D2 passing through the center O of the virtual circle E are taken from each land L1 and L2, and a diagonal line D is set as a composite vector of these diagonal lines.

Here, the diagonal lines D1 and D2 that determine the components of the composite vector are taken as straight lines passing through the center O of the virtual circle E from one point in the center of each of the lands L1 and L2, as shown in Figure (a). Alternatively, as shown in Figure (b), it may be a straight line passing through the center O of the virtual circle E from one point on the left end of land L1 and one point on the right end of land L2, or as shown in Figure (c). Alternatively, a straight line passing through the center O of the virtual circle E may be formed from a point near the center on the land L1 side and from a point on the right end on the land L2 side.

10...File 12...Spiral blade 14...Transition part 16...Shaft E...Virtual circle L...Land P...Floating vertex D...Diagonal line x...Offset amount

Claims (4)

A dental file with a spiral blade,
The cross section of the spiral blade is
a virtual circle constituting the outer shape of the spiral blade;
an arcuate land arranged on the virtual circle;
an acute-angled apex that is arranged to protrude from the center of the virtual circle and constitutes a cutting edge of the spiral blade;
The acute-angled apex is
a floating vertex located on the diagonal of the land and inside the virtual circle;
A dental file characterized in that only one floating apex is provided within the cross section. When there is one land, the diagonal line is a straight line passing through one point on the land and the center of the virtual circle,
Claim 1, wherein when the number of lands is two or more, the diagonal line is a straight line extending in a direction indicated by a composite vector of lines passing through one point on each land and the center of the virtual circle. Dental files listed. The dental file according to claim 1, wherein an offset amount by which the floating apex recedes inward from the virtual circle is within a range of 0.5% to 5% with respect to the diameter of the virtual circle. . The dental file according to claim 1, wherein the file is a nickel titanium engine file.

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