The present invention relates to a device for forming holes in, inter alia, gum and/or part of the jaw bone. The device comprises a cylindrical unit which is rotatable about its longitudinal axis and which is provided with forwardly directed parts that have cutting edges.

It is already known, in dentistry, to use hole-forming devices with forwardly projecting sawtooth-shaped parts which effect formation of a hole while the unit rotates in one direction. The known devices have disadvantages in that the saw teeth have become rapidly worn by interaction with the jaw bone and in that the hole formation is not sufficiently effective, because bone residues, bone chips and gum parts are easily left behind or spring back into the cavity of the hole, which makes difficult the continued use of the hole in the dental work. The rapid wear can make it necessary to change the tool/cylindrical unit during work on one and the same patient in whom a number of holes are to be formed. The wear is often caused by the fact that the gum and jaw bone parts are often arched in cross section, which has the effect that the sawtooth-bearing parts have to work in jaw bone before the hole is formed completely down through the gum arch in question. The present invention aims to solve these problems, among others, and proposes construction of a more durable instrument permitting longer use and guaranteeing smooth holes that are free of bone residues and gum.

What can principally be seen as characterizing a device according to the invention is that the forwardly directed parts are interconnected via arcuately curved recessed parts, in that the forwardly directed parts and also the recessed parts are provided with the cutting edges that include both forwardly directed and

laterally directed or obliquely forwardly directed cutting edge parts, and the latter cutting edge parts are designed to cooperate with the gum and/or part of the jaw bone in both directions of rotation in the forward and rearward rotation movements about the center axis of the cylindrical unit.

In further developments of the inventive concept, the rotation movements will be relatively small and, for example, have a magnitude situated in the range of slightly over zero to ca. 90°. Further developments of the inventive concept are set forth in the attached dependent claims.

By means of the invention, the cutting edge parts on the outermost parts of the forwardly directed parts can be allowed to become worn while a complete cutting ability still remains for the rear or inner cutting edge parts, which fact contributes to the prolonged useful life. The laterally directed or obliquely forwardly directed cutting edge parts also guarantee effective cutting-off of bone chips and gum parts, thus guaranteeing extremely smooth walls in the hole that is formed.

A presently proposed embodiment of a device having the features characteristic of the invention will be described below with reference to the attached drawing, in which:

Figure 1 shows a side view of the device in its entirety, with a targeting peg in the fully inserted position, and with the gum and jaw bone parts indicated symbolically,

Figure 2 shows, in cross section, the structure of the cutting edge-shaped parts,

Figure 3 shows a horizontal view of the cylindrical part from the end that has said cutting edge parts,

Figure 4 shows, in cross section, a segment indicating the structure of a cutting edge-shaped part,

Figure 5 shows a diagrammatic side view of the cylindrical unit's application to an arched gum and jaw bone, and

Figure 6 shows a side view of a protective cap for the cutting edge-shaped parts.

In Figure 1, a cylindrical unit is designated by 1. The unit has a length which, in a preferred embodiment, can lie within the range of 10-20 mm. In the illustrative embodiment shown, the cylindrical unit has a diameter D of ca. 5 mm. In its rear parts, the cylindrical unit is provided with an actuation member 2. The cavity in the cylindrical member and a cavity 3 in the actuation member 2 constitute bearing holes for a targeting or guiding peg 4 which has a cone shape at the front. The peg 4 is longitudinally displaceable in its bearing holes and can be removed from the unit and the actuation member, for example during hole formation, by being moved to the right in the figure. The peg has a shoulder 5 which limits the degree of insertion in the bearing holes. At the front, the unit 1 is provided with forwardly projecting parts, of which three parts, namely 6, 7, and 8, are shown in Figure 1. The number of forwardly projecting parts can be from four to eight, and in the case shown the number is six. The forwardly projecting parts are connected by arcuate recesses 9 and 10, of which two are shown in Figure 1. The forwardly projecting parts and the recesses are provided with cutting edge-shaped parts in accordance with what is explained below. A jaw bone 11 and a gum

12 are also symbolically indicated in Figure 1. The hole in the present case is to be made in the gum 12.

The forwardly projecting parts 6 and 7 are shown enlarged in Figure 2. Said parts 6 and 7 have cutting edges 13 and 14. Figure 2 also shows an arcuate recess 9 connecting the parts 6 and 7. The recess can be more or less semicircular in one embodiment. The recess too has a cutting edge, which is indicated by 15. The arrangement results in forwardly directed cutting edge parts that include the cutting edge parts 13 and 14. In addition, the middle part of the arcuate recess can be regarded as bearing a forwardly directed cutting edge part 16. The forward directions are indicated by arrows pointing straight to the left in Figure 2. The areas with laterally directed cutting edge parts or obliquely forwardly directed cutting edge parts are indicated by A and B, and the lateral and obliquely forward directions are indicated by arrows 17 and 18, respectively. The laterally directed cutting edge parts are indicated by 19 and 20. The obliquely forwardly directed arrows 17 and 18 can be divided up into vectors extending forward and to the side in a manner not shown here. The arcuate recess can be considered to have a middle area C which is provided with a forwardly directed cutting edge part.

Figure 3 shows the other forwardly directed parts 21, 22 and 23 with intermediate recesses 24, 25 and 26. Figure 3 also shows an angle α which can be present for example for the forward and rearward rotation movements executed in the directions of arrows 27 and 28. In accordance with the concept of the invention, the cylindrical part 1 is not to be rotated in just one direction, but can instead be subjected to said forward and rearward movements during the hole formation. The magnitude of the movements can be indicated by the magnitude of the angle α and can be in the range of slightly over 0 to 90°.

Figure 4 shows the configuration of the cutting edges of the cutting edge parts in question. The cutting edge parts can be generated by grinding 29 on the outside of the unit and possibly slight chamfering 30 on the inside.

Figure 5 shows the cooperation of the unit 1 with the arched gum 31 and arched jaw bone 32. It will be seen from Figure 5 that the pointed forwardly directed parts will abut the jaw bone 32 before the hole in its entirety has been completed in the gum 31. Despite the wear against the hard jaw bone and the resulting wear of the cutting edge parts at the points, the unit remains effective by virtue of the laterally directed or obliquely forwardly directed cutting edge parts and the edge parts within the area C which do not need to be rubbed against the jaw bone upon completion of the hole formation in the gum. The forward and rearward rotation movements of the unit 1 are indicated symbolically by 33 and 34 in Figure 5.

Figure 6 shows a protective cap 35 provided with a cavity 36 arranged to be engaged over the front of the unit 1 and in this way protect the sharp cutting edges.

In the figures, the center axis of the unit is indicated by 36. The cutting edge parts in the area C are also protected during the hole formation in the gum and can effectively contribute in the hole formation in the gum without becoming worn by interaction with the jaw bone.

The invention is not limited to the embodiment described above by way of example, and instead it can be modified within the scope of the attached patent claims and the inventive concept.