Depth-marking system arrangement for implant holes in the jawbone.

TECHNICAL FIELD The present invention relates to a depth-marking system arrangement in connection with the formation of implant holes in the jawbone. In this case, use is made of one or more band markings which are arranged on the tool being used, i.e. drill, countersinking drill etc., and, if appropriate, on the measuring instrument. Each implant is ascribed a nominal length which is less than the actual length of the implant.

PRIOR ART

It is well known to carry out work for forming holes in the human jawbone. The drill speeds are relatively high, for example 2500 rpm. During the drilling and hole-forming work, it is known to make use of marking systems comprising bands for determining the hole depth.

ACCOUNT OF THE INVENTION

TECHNICAL PROBLEM In connection with the work for forming holes for implants, a need has arisen for better functioning depth- marking systems. The invention aims to solve this problem among others.

It is now proposed that holes also be formed on the inner part of the jawbone, which is in contrast to the previous situation when implant work was carried out exclusively on and in the front parts of the jawbone. The inner parts of the jawbone are rich in nerves, and greater accuracy in respect of the depth of the holes formed must be possible, in order to ensure that nerves are not damaged in connection with the formation of the holes. It is important that the user should have accurate information relating to the varying depth of the respective hole as the work is progressing. The invention

solves this problem too.

The use of band markings which are known per se must be adapted to the high degree of accuracy of indication. It is important, in this respect, that no misjudgments should be possible on the part of the user.

The invention solves this problem too.

According to the invention, the novel depth- marking system is employed on the various tools and measuring instruments which are used in work for forming holes. It is important that band markings be in relation to the different functions of the tools and measuring instruments. The invention solves this problem.

Alternative uses of band markings in connection with different implant areas are additionally desirable. One particular use of the depth-marking system suits one user better than it does another user. The invention aims to solve this problem by offering different possibilities and formats for using the depth-marking system.

SOLUTION The feature which can principally be regarded as characterizing an arrangement according to the invention is that a first delimiting line or marking on a first band marking represents an indication of an absolute measurement of the hole depth. The absolute measurement in question in this case also includes an inner cone- shaped portion of the hole (corresponding to the cone- shaped part of the drill) . Also characteristic of the invention is the fact that a second delimiting line or marking on the said first band marking or a second band marking represents an indication of a position or a level which is reached by an upper part or upper surface of a unit arranged on the implant in question. This unit can consist of a cover screw, cap, hood, etc.

In one embodiment of the inventive concept, the first delimiting line or marking represents a lower delimiting line or marking on the band in question. The second delimiting line or marking can be represented by an upper delimiting line or marking on the said band in

question.

In further embodiments, two or more band markings can be arranged, with intermediate spacings between the band markings, on a tool in the form of one or more drills, by means of which the formation of the implant holes can be carried out. Each band marking can in this case be used for indication in conjunction with the formation of implant holes of different depths. In addition, two or more band markings can be arranged on a measuring instrument in the form of a measuring probe which can be applied in the implant hole which has been formed. Each band marking can in this case be used for indication in conjunction with the formation of implant holes of different depths. The system includes a countersinking tool. The countersinking tool is provided with a countersinking part, by means of which countersinking can be carried out in the upper part of the implant hole. The said counter¬ sinking part is related to the spacing between the first and second delimiting lines or markings, or the width of the band, in such a way that the aforesaid spacing or width essentially corresponds to the height of the countersinking part.

The drill which is used as the tool for forming the actual hole comprises a conical front part which is related to the measurement by which the nominal length of the implant is less than the actual length of the implant in such a way that the length of the said conical front part essentially corresponds to the aforesaid measurement.

In a further embodiment, each marking band is assigned an implant length specific to it. The second or upper delimiting line or marking on each band can in this case represent a function measurement which is important for the user and which considerably increases the clarity of indication, especially in connection with those countersinkings of the implant in the jawbone where the lower marking on the band is not so clearly seen during the work for forming the hole.

In a further embodiment, the band markings can be designed in such a way that only every second possible implant length is indicated. Each intermediate space between the depth markings forms a depth-marking band for each intermediate implant length. A particular feature in this case is that the difference between two implant lengths will be essentially the same size as the spacing between a connection plane on the upper part of the implant and the upper part of the said unit/cover screw which is applied or can be applied to the implant.

ADVANTAGES By means of what has been proposed above, it is possible to a large extent to prevent formation of bores which are too deep and which may damage the nerves and nerve systems in the jaw. During the entire hole-forming operation, the user can obtain clear information on the current depth of the bore. Since the depth-marking system can be applied over a large part of the range of tools and measuring instruments, there is no need for any converting from one meaning of the indication to another meaning. Another advantage is that band systems which are known per se can be used.

DESCRIPTION OF THE FIGURES

A presently proposed embodiment of an arrangement which has the characteristic features significant to the invention will be described hereinbelow with reference to the attached drawing, in which

Figure 1 shows, in longitudinal section, an implant applied in its final position in a jawbone, Figure 2 shows, in a side view, a first drill with a first diameter and with marking bands etched on the drill part.

Figure 3 shows, in a side view, a second drill with a second diameter which is greater than the diameter according to Figure 2, and with a corresponding arrangement of marking bands,

Figure 4 shows, in a side view, parts of a

measuring probe which is arranged with marking bands set in relation to the marking bands on the drills according to Figure 2 and 3,

Figure 5 shows, in a side view, a countersinking drill, in which the part carrying out the countersinking is set in relation to the relevant band on the drills according to Figures 2 and 3 and the measuring probe according to Figure 4, and

Figure 6 shows, from the side, a cover screw with a cover part which is set in relation to the connection plane of the implant according to Figure 1, and a plane which represents the top side of the relevant band.

DETAILED EMBODIMENT

Figure 1 shows an implant (implant screw) 1 which is known per se and which is applied in a jawbone symbolized by 2. The implant has a nominal length or height L which is slightly less, by a length 1, than the actual length L' of the implant. The measurement 1 can be, for example, between 0.1 and 0.2 mm. The implant 1 comprises a screw part la provided with an external thread, and a nut part lb at the upper part of the implant.

Figure 2 shows a first drill 3 with a drill part 3a and an attachment part 3b for attachment to a suitable drilling machine (not shown) . Marking bands A, C, E and G are arranged on the drill part 3a. Each band, which is shown dark in Figure 2, is assigned its own implant length. Thus, the band C is assigned the implant according to Figure 1. The bands are arranged one above the other, with intermediate spaces B, D and F, respectively. The bands are marked by etching, mechanical marking, etc., which can be carried out in a manner known per se. It is possible per se to regard the said inter¬ mediate spaces as bands themselves, and the said bands as intermediate spaces. In Figure 2, the jawbone is indicated or symbolized by 2', and a hole formed in the jawbone by the drill 3 is partially shown by 4.

Each band has a first or lower delimiting line or

delimiting marking which represents an absolute measure¬ ment of the hole depth in question. The said lower line or marking, for example the line or the marking for the band C, is shown by 5. Each band also has a second or upper delimiting line or delimiting marking, which is shown by 6 in the case of band C. The absolute measure¬ ment, indicated by the band C, to the hole bottom, which is symbolized by a line 7, is shown by c in Figure 2. The absolute measurement shown by the band A is indicated by a, the absolute measurement shown by the band E is indicated by e, and, finally, the absolute measurement shown by the band G is indicated by g. It will be seen that the bands A, C, E and G can thus be assigned to different implant lengths. The second or upper delimiting line represents an indication of a position or a level to which, or to immediately below which, an upper part of a cover screw (cf. Figure 6) extends when the implant 1 according to Figure 1 assumes its final position in the bone 2. The said position or level above the bottom 7 of the hole exhibits a distance b for band A, a distance d for band

C, a distance f for band E, and a distance h for band G.

Figure 3 shows a second drill which is of a construction corresponding to that of the drill 3 in Figure 2, but having a diameter D' which is greater than the corresponding diameter of the drill 3. The drill 3 represents a preliminary drill, and the drill 8 a final drill, the said drill 8 being used to form a hole 9, in the wall of which the implant is screwed tight into the bone material via the external thread of the implant, the diameter D' ' of which slightly exceeds the diameter D' . The drill 8 exhibits a marking band system corresponding to that of the drill 3. The correspondence is shown in the figure by means of horizontal lines, the upper horizontal line having been designated 10.

Figure 4 shows a measuring instrument/measuring probe, the end 11a of which has been provided with marking bands corresponding to those of the drills according to Figures 2 and 3. The correspondence is

symbolized by means of horizontal lines running towards the drill 8, the upper horizontal line having been shown as 12. The measuring instrument has a cone-shaped end part lib which corresponds to the cone-shaped parts 3c and 8a of the drills 3 and 8, respectively.

Figure 5 shows a countersinking drill 12 which has a part 12a which produces a cone-shaped portion 13 in the jawbone 2 ' ' , the said cone-shaped portion forming the countersunk portion. The tool 12 also comprises a guide part 12c, the lower part of which can cooperate with the hole wall at the lower, cone-shaped part 14 of the hole formed by the drill. The said countersinking portion 12a on the tool has a length/height L' ' which corresponds essentially to the width of the relevant band, i.e. band C in the case illustrated.

Figure 6 shows the design of a unit in the form of a cover screw 15, with a part 15a which has an external thread by means of which the cover screw can be screwed into an internal thread lc in the implant according to Figure 1. In addition, the cover screw has a cap-shaped part 15b which covers the nut part lb when the cover screw is in position on the implant.

When the implant according to Figure 1 takes up a [lacuna] in the implant hole, which in Figure 1 is symbolized by its cone-shaped part 14', an upper part or upper surface 15b' of the cap assumes a position or a level 16 which substantially coincides with, or is situated immediately below, the level of the second delimiting line or delimiting marking on the relevant band, in this case band C.

The cone-shaped part of the drill, measuring instrument and hole has a depth 1' . A connection plane for or on the implant is shown by 17. A plane 18 which marks the said height 1' for the cone-shaped parts of a drill, measuring instrument, etc., is indicated by 18.

As a result of the above, implants can be placed where the drilling depth is limited and where it is important to know exactly how deep one has drilled. In this connection it is also possible to use computed

tomography in order to determine the distance from the bone surface to the nerve which is located at certain sites in the dentine. In accordance with the above, use is made of a band marking or band markings designed such that the lower edge of each band gives:

1. The absolute measurement, for example c for band C, in mm.

2. The measurement is the distance from the tip (cf. the line 7) of the prepared hole to the upper connection plane (17) of the implant.

3. The speci ied measurement is the nominal length of the implant, and for the functioning of the system it is assumed that the implant has a nominal length (L) which is somewhat shorter than the actual length (L') . This difference corresponds to the conical part (i.e. the distance 1') of the preparing drill (3 or 8).

The upper part of each marking band (band C, for example) for a specific implant length (for example, the length of the implant according to Figure 1) gives:

1. An indication of the position of the implant once the so-called cover screw (according to Figure 6) has been applied.

2. Furthermore, in addition to giving a function measurement which is important for the user, this increases considerably the clarity of the indication. This is due to the fact that the implant is often countersunk in the bone such that the lower marking is not so clearly seen. In one embodiment of the inventive concept, it is possible, with the aid of the arrangement according to the invention, to mark only every second implant length and to let the intermediate space (B, D and F) between two coloured bands (A, C or C, E or E, G) represent depth-marking bands for this intermediate implant length. In order for this to function, the difference between two implant lengths must be the same size as the distance between the connection plane (17) of the fixture and the distance to the upper part of the cover screw (cf. the

plane 16) .

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