WO1999060945A1

WO1999060945A1 - Assembly of drills for forming a hole in a tooth root and method for placing a canal post in a tooth root

Info

Publication number: WO1999060945A1
Application number: PCT/NL1999/000217
Authority: WO
Inventors: Hidde Doornbusch
Original assignee: Hidde Doornbusch
Priority date: 1998-05-22
Filing date: 1999-04-14
Publication date: 1999-12-02
Also published as: NL1009247C2; AU3346599A

Abstract

The present invention relates to a dental drill for drilling a hole in a tooth or molar, the drill being provided on the underside with a non-cutting stub, the diameter of which is less than the diameter of the cutting section of the drill. The stub on the underside of the drill guides the dental drill through a prepared canal in the tooth or the molar.

Description

ASSEMBLY OF DRILLS FOR FORMING A HOLE IN A TOOTH ROOT AND METHOD FOR PLACING A CANAL POST IN A TOOTH ROOT

The present invention relates to an assembly of drills for forming a hole in the root of a tooth or a molar, which hole serves to accommodate a canal post.

The drill according to the present invention is particularly suitable for safely clearing out and preparing a root canal in a tooth or a molar, in order for a root canal post to be placed in the tooth or molar, on which post an artificial crown can then be anchored. In the prior art, it is known to use a canal post in the root canal of a tooth or a molar to provide an anchor for an artificial crown. The artificial crown is generally attached to the root canal post with the aid of cement.

To ensure that the root canal post is well anchored in the root for a long time, the shape of the root canal post is preferably matched to the shape of the roots of teeth or molars. These roots are relatively wide at the top and taper slightly towards a rounded underside. That section of a root canal post which is to be introduced into the root is therefore preferably relatively wide at the top and, like the root itself, tapers towards the underside.

The diameter of that section of the root canal post which is placed in the root may, for example, decrease in steps. In that case, the root canal post, even if it moves a relatively short distance in the longitudinal direction, remains secured in the root with as high a retention level as possible. Stepped root canal posts of this nature are placed in stepped holes with a corresponding cross section. To make a stepped hole in the root canal, it is necessary to use a stepped drill. A drill of this nature is known, inter alia, from French Patent 1,276,769. This document discloses a stepped drill with three steps. On the underside, the drill is provided with a non-cutting guide or stub. The diameter of this stub is matched to the size of the root canal in the root. During drilling, the drill is guided through the root canal, towards the apex of the root, with the aid of the stub. In practice, however, it has proven extremely difficult to use a stepped drill of this nature to drill precisely in the direction of the existing root canal in the tooth or the molar. Even if advanced equipment is used, there is a high risk of the stepped drill not following the root canal and drilling at an angle into the root. This means that there is a high risk of perforations (i.e. a high risk of the drill drilling through the wall of the root).

In order to ensure that a root canal post can be placed in the prepared root canal with sufficient retention, it is necessary to drill a sufficiently deep hole in the root. This involves running the abovementioned risk of perforations being formed. If, to prevent the possibility of a perforation being formed, the drill according to the prior art, for safety reasons, is used to drill a relatively shallow hole in the root, the root canal posts could not be arranged so far into the prepared canal. In this case, the retention of the root canal post in the prepared root canal is not optimum.

In view of the drawbacks of the drills according to the prior art, the object of the present invention is to provide an assembly of the type mentioned in the preamble which makes it possible to drill relatively deep holes in roots of teeth or molars while reducing the risk of the drill selecting an undesirable direction and drilling through the wall of the root of the tooth or the molar.

This object is achieved according to the invention by the fact that the assembly comprises a preliminary drill which is essentially cylindrical in form, and a finishing drill, which is provided, on the underside of the cutting section, with a non-cutting stub, the smallest diameter of the cutting section of the finishing drill being larger than the diameters of the preliminary drill, and the diameter of the stub essentially corresponding to the diameter of the preliminary drill.

According to the invention, it is possible for the diameters of the preliminary drill and the stub to be 0.5-1 mm. It is advantageous for the diameters of the preliminary drill and the stub to be 0.6-0.8 mm and preferably 0.7 mm. According to the invention, a relatively thin, standard dental drill can be used as the preliminary drill. This thin dental drill can be guided along a canal which has already been endodontically prepared, until it has reached the desire depth, in the correct direction in the root of a tooth or molar. The root canal can be widened much more accurately, and therefore more safely, using the relatively thin preliminary drill than using the relatively thick drill according to the prior art. The risk of the relatively thin preliminary drill not following the root canal and drilling into the root at an angle is much less than with the relatively thick drill according to the prior art. This means that the risk of perforations when using the relatively thin drill is also much less. The preliminary drilled hole can then be used by the finishing drill according to the present invention. The diameter of the stub which is attached to this finishing drill corresponds to the diameter of the preliminary drill. As a result, the stub can serve as a guide for the finishing drill. This means that the longitudinal axis of the final hole substantially corresponds to the longitudinal axis of the preliminary drilled hole. Since the stub itself is non-cutting, the drill cannot reach further than the underside of the preliminary drilled hole. The hole is pre-drilled accurately and safely using the relatively thin preliminary drill which is easy to handle. Although the finishing drill will reach into the bottom of the preliminary drilled hole, the depth of the preliminary drilled hole will remain unchanged. This considerably reduces the risk of perforations while nevertheless allowing a relatively deep hole to be made in the root of the tooth or the molar.

Furthermore, there is no possibility, when drilling the final hole using the second drill, of drilling a hole whose longitudinal axis deviates from that of the first, preliminary drilled hole. If this were to be the case, there would be a risk of the space which has been drilled in the tooth or molar not being completely filled by a root canal post which can subsequently be arranged in the hole.

According to the present invention, it is possible for the length of the stub, as measured in the longitudinal direction of the drill, to be 0.5-5 mm. It is advantageous for the length of the stub, measured in the longitudinal direction of the drill, to be 1- 3 mm, and preferably 2 mm.

With a length of this nature, the stub is able to guide the finishing drill correctly through the preliminary drilled hole without impeding correct operation of the finishing drill. It is possible for the finishing drill to comprise an essentially cylindrical cutting section. It is also possible according to the invention for the diameter of the finishing drill to increase conically or in steps from the non-cutting stub.

These measures ensure that the shape of the hole which can be drilled with the finishing drill in the longitudinal direction of the root is matched to the diameter of the root. This means that the diameter of the hole which can be drilled using the finishing drill decreases from the relatively wide top of the root towards the thin tooth apex. If a canal post which is adapted to this shape is placed in the root, the material of the root is used to optimum effect. Furthermore, it is possible, according to the invention for the assembly furthermore to comprise a canal post, having a first end which, in use, is arranged in the hole which is to be formed using the drills the canal post being provided at the said first end with a projection, the dimensions of which substantially correspond to the dimensions of the stub. As will be explained in more detail below, the shape of the hole which is drilled in the root is known. Since the dimensions of the stub on the finishing drill are matched to the dimensions of the preliminary drill, and since the stub on the finishing drill is used as a stop, the shape of the hole drilled in the root is clearly determined by the depth reached with the preliminary drill. It is possible to adapt the dimensions of the canal post to the shape of the drilled hole. This results in the drilled hole being essentially completely filled with the canal post.

The invention furthermore relates to a method for placing a canal post in a root of a tooth or a molar, the canal post being placed in a hole which has been drilled in the root with the aid of an assembly according to the invention. The method according to the invention is characterized in that a preliminary drill is used to widen the root canal in the root, in the direction of the tooth apex, and a finishing drill is then used to widen the preliminary hole which has been drilled in the root in the radial direction, while the preliminary drilled hole is not drilled further in the axial direction.

In this case, it is possible for the finishing drill to be guided through the preliminary drilled hole in the root with the aid of a non-cutting guide at the end of the finishing drill, the diameter of the guide essentially corresponding to the diameter of the preliminary drill, and for the guide at the end of the finishing drill to be used as a stop, the finishing drill being guided into the preliminary drilled hole until the guide reaches the underside of the preliminary drilled hole. These measures ensure that a deep hole can be safely pre-drilled in the root of the tooth. The deep hole is then used in order to guide the finishing drill relatively far into the root. This finishing drill is guided by the preliminary drilled hole. The finishing drill cannot make the preliminary drilled hole deeper. This means that the finishing drill cannot endanger the hole which has been drilled safely. It should be noted that American patent 4,854,871 discloses a method and a device for flattening the top side of a root of a tooth or a molar. According to this American patent, a drill is used to drill out the root canal to the final depth in a single operation. This drilled canal can be used to guide an instrument which is used to flatten the top side of the root. The flat part which is formed on the top side is used to provide good support for the canal post which is placed in the hole.

A further difference between the method and device according to American patent 4,854,871 and the present invention is that according to the present invention a relatively deep hole is drilled with both the preliminary drill and the finishing drill. According to the invention, the finishing drill also reaches all the way to the end of the preliminary drilled hole. According to the abovementioned American patent, the instrument for flattening the root is guided into the root via a section of the drilled hole. The instrument does not reach as far as the bottom of the drilled hole. A second difference which can be noted is that the shape of the hole in the root, according to the present invention, is entirely known, since the guide stub at the end of the finishing drill is used as a stop. Since this shape is known, the shape of the canal post can be selected in such a way that the canal post fills up the drilled hole.

The present invention will be explained in more detail with reference to three Figures, in which:

Figure 1 shows a cross section through a root of a tooth or a molar in which a hole has been pre-drilled using a cylindrical preliminary drill.

Figure 2 shows a cross section through the root of a tooth or a molar in accordance with Figure 1 in which a stepped hole has been drilled with the aid of a finishing drill according to the present invention.

Figure 3 shows a cross section through the root of a tooth or a molar in accordance with Figures 1 and 2 in which a stepped root canal post has been arranged.

Figure 4 shows a cross section through a root of a tooth or a molar in which a cylindrical root canal post has been arranged. Figure 5 shows a cross section through the root of a tooth or a molar in which a conical root canal post has been arranged.

Figure 1 shows a cross-sectional view of a root 1 of a tooth or a molar. This root 1 is embedded in a jawbone 2. A root canal 3 runs through the root 1 towards the jaw 2. Before a root canal post can be placed in the root, an endodontic treatment (nerve treatment) has to be carried out, or a previously fitted root canal filling has to be removed.

In order to be able to place a root canal post in the root 1, firstly a straight, thin preliminary drill 4 is used to drill a straight hole 10 in the root 1. This preliminary drill 4 comprises an attachment 5 on the top side allowing the drill 4 to be coupled to a treatment instrument (angle handpiece). This preliminary drill 4 can be used to safely pre-drill a straight hole in the root 1. This is possible, for example, by means of guidance along a canal which has already been endodontically prepared. On the underside, the preliminary drill 4 may be provided with a non-cutting guide 40. With the aid of this guide, the preliminary drill 4 is guided through the root canal 3 towards the apex of the root 1.

Figure 2 shows the situation where a stepped hole 9 has been made in the root 1 using a stepped finishing drill 6 according to the present invention. It can be seen that the drill 6 comprises a plurality of steps 7, 71, 72 with a cutting outer side. On the underside, the drill 6 is provided with a non-cutting, for example smooth, stub 8. During drilling, this smooth stub 8 is guided through the preliminary drilled hole 10, so that the drill 6 can be guided along a straight path through the canal which has been prepared in the root 1. Since the stub 8 is non-cutting, the drill 6 will only be able to extend as far as the bottom of the drilled hole 10. It is therefore impossible for the drill 6 to continue onwards and drill through the wall of the root 1. This reduces the risk of perforations. It should be noted that the diameter of the stub 8 is at least slightly smaller than the diameter of the preliminary drill hole 10.

It can also be seen in Figure 2 that the diameter of the stub 8 is smaller than the diameter of the smallest step 72 of the drill 6.

Figure 3 shows the situation in which a root canal post 11 with a stepped underside has been arranged in the stepped hole in the root 1. Since the shape of the underside of the root canal post 11 is matched to the shape of the stepped drill 6, the root canal post 1 1 can be reliably and fixedly secured in the root 1. After this root canal post 11 has been placed in the root 1, a crown 12 can be constructed around the top of the root canal post 11.

According to the invention, the diameter of the stub 8 at the end of the finishing drill 6 is at least slightly smaller than the diameter of the cutting section of the drill which has the smallest diameter. As an alternative to being stepped, as shown in Figures 2 and 3. the finishing drill 6 may also be of cylindrical design.

Figure 4 shows the situation in which a canal post with a cylindrical cross section has been placed in the root 1. A canal post of this nature is placed in a hole which has been drilled with the aid of a finishing drill 6 of corresponding cylindrical form. Similar arrangements apply to the situation illustrated in Figure 5. A canal post with a conical underside has been placed in a hole which has been drilled using a drill of corresponding conical form.

In order to be able to know how deep the preliminary drill 4 has drilled into to the root 1 , the outer wall of this preliminary drill may be provided with markings, making it possible to check whether the drill has drilled sufficiently deep into the root.

With regard to the above text, the dental drill according to the invention may be a diamond drill or may be made from any other suitable material. The root canal posts referred to in the above description are made, for example, of titanium or another suitable material.

It should be understood that the above description of the drawings serves only to illustrate the present invention.

Claims

1. Assembly of drills (4, 6) for forming a hole in the root (1 ) of a tooth or a molar, which hole serves to accommodate a canal post (11), characterized in that the assembly comprises a preliminary drill (4) which is essentially cylindrical in form, and a finishing drill (6), which is provided, on the underside of the cutting section, with a non-cutting stub (8), the smallest diameter of the cutting section of the finishing drill (6) being larger than the diameter of the preliminary drill (4), and the diameter of the stub (8) essentially corresponding to the diameter of the preliminary drill (4).

2. Assembly according to Claim 1, characterized in that the diameters of the preliminary drill (4) and the stub (8) are 0.5-1 mm.

3. Assembly according to Claim 1 or 2, characterized in that the diameters of the preliminary drill (4) and the stub (8) are 0.6-0.8 mm, and preferably 0.7 mm.

4. Assembly according to one of the preceding claims, characterized in that the length of the stub (8), measured in the longitudinal direction of the drill (6), is 0.5-

5 mm.

5. Assembly according to one of the preceding claims, characterized in that the length of the stub (8), measured in the longitudinal direction of the drill (6), is 1-3 mm, preferably 2 mm.

6. Assembly according to one of the preceding claims, characterized in that the diameter of the finishing drill (6) increases conically or in steps from the non-cutting stub (8).

7. Assembly according to one of the preceding claims, characterized in that the assembly furthermore comprises a canal post (11), having a first end which, in use, is arranged in the hole which is to be formed using the drills (4, 6), the canal post (11) being provided at the said first end with a projection, the dimensions of which substantially correspond to the dimensions of the stub (8).

8. Method for placing a canal post (11) in a root (1) of a tooth or a molar, the canal post (11) being placed in a hole which has been drilled in the root (1) with the aid of an assembly according to one of the preceding claims, characterized in that:

- a preliminary drill (4) is used to widen the root canal (3) in the root (1), in the direction of the tooth apex, and

- a finishing drill (6) is then used to widen the preliminary hole which has been drilled in the root (1) in the radial direction, while the preliminary drilled hole is not drilled further in the axial direction.

9. Method according to Claim 8, characterized in that the finishing drill (6) is guided through the preliminary drilled hole in the root (1) with the aid of a non-cutting guide (8) at the end of the finishing drill (6). the diameter of the guide (8) essentially corresponding to the diameter of the preliminary drill (4).

10. Method according to Claim 8 or 9. characterized in that the guide (8) on the end of the finishing drill (6) is used as a stop, the finishing drill (6) being guided into the preliminary drilled hole until the guide (8) reaches the underside of the preliminary drilled hole.