DE19541032A1 - Dental tool - Google Patents

Abstract

A tool drivable by a sonic or ultrasonic dental holder for working on dental cavities, in which a working head (1, 21, 41, 51) is secured or can be releasably secured to an adapter shaft (2, 22, 42, 52), the working surfaces of which facing the inner surfaces of the cavity are coated with abrasive material and the shape of which is matched to that of the cavity in such a way that several to all differently oriented inner surfaces of the cavity can be simultaneously treated. The tool makes it possible in particular to make a recess in two sides of two abutment teeth facing a gap in the teeth for a bridge, into which can be inserted shoulders of a bridge of suitable size.

Description

The present invention relates to dental tools, in particular by sonic or ultrasonic dental handpieces drivable tools for processing Tooth cavities.

In conventional cavity processing, access to the carious is first given Places are opened and the carious lesions are excavated. Then one Resistance and retention form prepared and finally the cavity is finished. The preparation and finishing of tooth cavities is conventionally carried out with rotating instruments. However, rotating instruments have crucial ones Disadvantage. Due to the high efficiency, it is not possible to destroy to avoid healthy dental material. Even with small carious spots it is Provision of large access channels required. It comes from the high friction to a strong heat development, the supply of large amounts of Requires cooling feet. The head of rotating instruments must therefore be dimensioned large in order to simultaneously keep the coolant nozzles and the drive to accommodate the drill. This improves the view and freedom of movement of the Doctor's limited. In the case of rotating instruments, there is also the angle between the drill axis and the handpiece fixed what the Possible uses of these instruments are further restricted. In the approximal area the preparation and especially the finishing by the neighboring tooth become strong with special needs. This will damage the neighboring tooth in most cases. That's why it has been proposed to finish after conventional coarse finishing paration with the help of hand instruments. As a result, however demonstrated that hand instruments leave unacceptable marginal destruction. On the other hand, flexible diamond-coated files are known for finishing, but it does through the tip of the file, when using a long stroke, to injure the Enamel casing can come. A reduced stroke can do this phenomenon at most reduce, but not eliminate. It also comes with this Method for unacceptable marginal defects. In some cases, this can happen  re-refinement with a rotating diamond can be reduced. In However, this approach is in the direction of the aproximo-cervical curvature Not possible due to lack of space.

The time required for cavity processing, especially in the approximal area, is high when using conventional dental tools. This is because that the rotating instruments may need to be replaced, or that has to be refinished.

It is therefore an object of the present invention to provide a tool for machining To provide tooth cavities that the neighboring tooth does not in the approximal area damaged, is still hindered by this and that with easy handling quick treatment allowed and excellent edge quality under the greatest possible protection of healthy tooth material is guaranteed.

This object is achieved according to the invention with a sound or ultrasound Dental handpiece driven tool for processing tooth cavities according to Claim 1 solved.

The tools according to the invention are self-guiding when machining cavities and self-limiting and allow cavity processing with a high Edge quality, especially in the approximal cavity area. Because of the special Several cavity inner surfaces can be machined simultaneously. Furthermore, the tools according to the invention are easy to handle and operate through a modified machining process to a considerable time saving.

The tools according to the invention work with only a small vibration moment, whereby the processing block depending on the dental handpiece at a Force application of, for example, over 1.5 N comes to a standstill. This will a destructive or thermally damaging preparation technique automatically prevented. Due to the low moment, softer carious is preferred Tooth material removed. In contrast, destructions on healthy  Tooth material largely prevented. This doesn't just damage the body Preparing tooth practically excluded: thanks to the special instruments the neighboring tooth cannot be prepared. They also work Tools according to the invention are often used in conventional preparation observed excessive expansion of the cavity.

The tools according to the invention enable a modified procedure in the Cavity processing. The sequence does not consist of the like in the prior art four stages: (1) opening, (2) excavation, (3) preparation of the resistance and Retention form and (4) finishing. Rather, it is limited to three levels: (1) Open, (2) definitive preparation with simultaneous finishing and (3) excavation. Refinishing is only necessary in rare cases. Thanks to the variable intensity The work movement can be done with a single preparation and finishing Instrument set can be accomplished without relying on different diamond grit sizes and thus have to fall back on several instrument approaches. The Use of the air pressure connection or the ultrasound approach in the dental Unit offers the advantage that conservative cavities are prepared with micromotors and can be excavated, the one normally reserved for the Airotor Air pressure connection, or the Ultra intended for tartar removal sound connection is occupied with the tool according to the invention. Will be on the first Micromotor clamped a red contra-angle with a spherical diamond and becomes the second micromotor with a round bur in the blue contra-angle is not a single change of instruments during the entire treatment necessary. In addition to the considerable reduction in time, these factors allow an optimal one Ergonomics.

In an advantageous embodiment, the areas of the processing block have the come into contact with the neighboring or opposite teeth or restorations can, areas that are non-abrading. This will cause damage other teeth and restorations completely excluded by these areas. In another embodiment, the adapter shaft can have an inner channel and have an outlet opening for coolant to prevent heat build-up  prevent sanding dust or the areas to be processed Add liquid and / or auxiliary materials. Furthermore, it is conceivable that the Work surfaces of the adapter adapted to the handpiece with the adapter shaft Stand the processing block at an angle to the longitudinal axis of the handpiece. There optimal ergonomics of the tool can be achieved. Still is it is possible that the processing block has a surface to be specifically machined optimally adapted shape. The work surfaces of the work according to the invention stuff with natural or artificial diamond grain, cubic boron carbide or similar abrasives, the grain size depending on the indication can be different.

Various embodiments of the invention are described below Tools described using drawings. Show it:

FIG. 1a is a side view of a first embodiment of a tool according to the invention;

FIG. 1b is a side view of a second embodiment of the tool according to the invention;

Fig. 2 is a perspective a) front or b) rear view of the tool.

Figs. 3a to f transverse and longitudinal sections of further modified embodiments of the tool;

Fig. 4 shows a first embodiment of a coupling of the tool according to the invention; and

Fig. 5 shows a second embodiment of a coupling of the tool according to the invention.

A tool according to the invention is shown in FIG. 1a. A processing block ( 1 ) is arranged at one end of an adapter shaft ( 2 ). The connection between processing block ( 1 ) and adapter shaft ( 2 ) can be provided by any connection method, such as soldering, gluing and the like, as long as the connection has sufficient strength for the desired purpose. In addition, it is possible that the unit consisting of machining block and adapter shaft is manufactured in one piece without a connection between the machining block ( 1 ) and the adapter shaft ( 2 ) being necessary. The processing block ( 1 ) comprises an essentially cuboid shaped piece which has work surfaces which are coated with abrading material. The adapter shaft ( 2 ), on which the processing block ( 1 ) is provided, comprises a curved tube which, if necessary, tapers in the direction of the processing block. The curvature of the tube is designed such that two essentially straight regions of the adapter shaft are at an angle to one another. The two essentially straight areas of the adapter shaft have a different length, the shorter area being connected to the processing block. An inner channel ( 3 ) extends in the adapter shaft ( 2 ). The inner channel ( 3 ) is designed so that a liquid can be directed to the surfaces to be processed. For this purpose, the adapter shaft ( 2 ) has a slot-shaped outlet opening ( 4 ) in the vicinity of the processing block ( 1 ). The adapter shaft ( 2 ) is coupled to a conventional dental handpiece (not shown) using a connecting device which is customary for dental handpieces. In this embodiment, since the processing block and the adapter shaft form a unit, the entire unit must be processed or disposed of after the diamond grain has been abraded. It therefore makes sense to construct not only the machining block but also the adapter shaft at low cost.

The embodiment of the processing block ( 1 ) shown in FIG. 1b and the outline of the adapter shaft ( 2 ) are similar to the embodiment shown in FIG. 1a. The difference is a lockable rotating mechanism ( 5 ) with which the adapter shaft can be broken down into two parts. The first part comprises the processing block ( 1 ). A second part ( 7 ) comprises the part of the adapter shaft which is coupled to the dental handpiece. In this embodiment, the processing block can be separated by releasing the lockable rotating mechanism ( 5 ). As soon as it is possible to dispose of the processing block separately, the adapter shaft can be of very high quality and expensive construction, since it rarely has to be changed. In contrast, in this embodiment, the machining block should be able to be manufactured as inexpensively as possible.

In Fig. 2, a processing block according to the invention is shown in a perspective view from (a) in front or from (b) behind. The processing block ( 21 ) consists of an essentially cuboid shaped piece. The cuboid shaped piece has a cylindrical bore ( 25 ) on the upper end face ( 23 ). Three side surfaces of the processing block ( 21 ) are designed as working surfaces with abrading material. The lower end face (not shown) of the processing block is also covered with abrading material. All other surfaces, ie the upper end surface and a side surface, are designed as non-abrasive surfaces. A slot ( 29 ) perpendicular to the longitudinal axis of the processing block is provided on the side surface ( 27 ). This slot ( 29 ) serves as a retention element for the adapter shaft, which is introduced into the machining block through the cylindrical bore ( 25 ). For this purpose, the slot ( 29 ) extends from the surface ( 27 ) substantially perpendicular to the cylindrical bore ( 25 ) and opens into it. The angle α, which is formed between two adjacent side surfaces, can be adapted to the respective indication. A typical value for a processing block for an approximal cavity is α = 120 °. The cuboid processing block is used for cavity processing in the proximal area. By designing the machining block according to the invention, the neighboring tooth cannot be damaged, since the surface facing the barzahn is not abrasive. The processing block shown in FIG. 2 is suitable for use in the embodiment shown in FIG. 1b.

Fig. 3a-d show other examples of cross sections of processing blocks. The cross section can have a trapezoidal shape, possibly with rounded corners ( FIG. 3a). A semicircular cross-sectional shape ( FIG. 3b), an essentially rectangular cross-section with rounded corners ( FIG. 3c) and an elliptical cross-section ( FIG. 3d) are also possible. The cylindrical bore is preferably in the center of the cross-sectional shape. However, an arrangement of the cylindrical bore in another area of the cross-sectional shape is also possible. The processing blocks according to the invention can furthermore have an essentially rectangular ( FIG. 3e) and a semi-elliptical or parabolic longitudinal section shape ( FIG. 3f). In the case of a parabolic longitudinal section shape, the machining block is not only ideal for machining cavities, but also for machining the cavity edges or the filling surfaces.

FIG. 4a shows an embodiment for a substantially form-fitting releasable connection between Adaptierschaft (42) and a working jig (41). In this embodiment, a cylindrical bore ( 43 ) milled from above into the processing block is provided, which is delimited at the bottom by a slot ( 44 ) similar to that in FIG. 2b, which is at an angle of 90 ° to the drilling axis. The length of the slot ( 44 ) is slightly wider than the diameter of the bore ( 43 ). As can be seen in the top view ( FIG. 4b), the entrance of the bore has one or more guide grooves ( 45 ). The end of the adapter shaft facing the machining block consists of a hollow, slotted tube of the same or slightly larger diameter than the bore in the machining block. This tube ( FIG. 4d) tapers conically at one end and has a thickening at the tip, such as an "envelope fold". The tube can be made from resilient metal. A guide rail ( 46 ) is provided on the outer wall of the tube, which fits into the guide groove ( 45 ) of the processing block ( 41 ). For the connection between Bear processing block ( 41 ) and adapter shaft ( 42 ), the slotted tube, possibly with special pliers, pressed together and inserted into the bore of the processing block until it engages with its "envelope fold" in the slot ( 44 ). The position angle of the machining block with respect to the shaft axis and the protection against unintentional rotation of the machining head about its axis is ensured with the guide rail ( 46 ) in connection with the corresponding guide groove ( 45 ). In order to release the connection, the slotted tube must be compressed, if necessary again with special pliers, whereupon it can be pulled out of the bore of the processing block.

In Fig. 5a shows a second embodiment for a frictional, detachable connection between working jig (51) and Adaptierschaft (52) is shown. In this embodiment, the processing block also has a cylindrical bore ( 53 ) from above into the processing block. The end of the adapter shaft facing the machining block consists of a hollow, slotted tube ( FIG. 5d) of the same or slightly larger diameter than the bore in the machining block. This tube has parallel walls ( Fig. 5d) and can be made of resilient metal. For the connection between the processing block ( 51 ) and the adapter shaft ( 52 ), the slotted tube is pressed together, if necessary with special pliers, and inserted into the bore of the processing block. In order to release the connection, the slotted tube must be compressed again, if necessary using special pliers, after which it can be pulled out of the hole in the machining block.

The shape of the machining block corresponds to the shape of a tooth cavity fits so that several surfaces of a tooth cavity can be machined simultaneously. Here the processing block can be designed as a universal processing block. He is so small that it fits into the smallest usual cavities. If with one Such small universal machining blocks can process large cavities the universal machining block must be moved around in the cavity, so that different work surfaces or groups of work surfaces take effect one after the other. But it is also possible and preferred to have a family to provide processing blocks that differ in size and shape che cavity types are adapted.

In the following, the shape of the processing block is generally described will. The surface facing the adapter shaft is called the proximal surface designated. The surface facing away from the adapter shaft is called the distal surface net. All other surfaces are called side surfaces.

An axis extending through the proximal surface and the distal surface is called  Designated longitudinal axis. The processing block can be its largest dimension (Length) in the direction of the longitudinal axis. The length is preferably 1 to 7 mm, especially 2 to 4 mm. The large dimension of the processing block in one die The transverse plane intersecting the longitudinal axis orthogonally is called the width. The Width can be the same over the entire length of the processing block. she can but also vary over the length. It can go from the proximal surface to the distal surface decrease (e.g. with a paraboloid of revolution towards zero). But it can also from increase the proximal surface towards the distal surface. The ratio of length to Width (in the case of a width variation over the length: to the maximum width) of the Be work block is preferably 1: 1 to 4: 1 and especially 1: 1 to 3: 1.

The largest dimension of the processing block in an orthogonal to the width Direction in the transverse plane is called "thickness". This can (like the width) vary over the length of the processing block or remain the same. The relationship The (maximum) thickness to the (maximum) width is preferably 1: 3 to 3: 1 and especially 1: 2 to 2: 1.

The processing block is not only suitable for processing cavities, but also also for machining cavity edges and as a secondary indication also for Grinding surfaces.

In one embodiment, the processing block corresponds to the front view a cuboid with a semicircular base. In horizontal section it looks like one isosceles trapezoid, which optimally cutting the melting jacket allows prisms. In addition to the periphery, the diamond coating includes the pulpa facing surface. The diamond coating can be a grain in the range of 5-200 µm, preferably 20-60 µm. The area facing the interdental space is smoothly polished, which excludes destruction on the neighboring tooth. For efficient An intra-water spray can be used to cool and remove the grinding sludge cooling can be provided. Furthermore, an optimal view via an integrated Illumination of the handpiece can be ensured.  

In a further embodiment, which are used as a universal version the working end consists of a cuboid with rounded transitions from the axial walls to the cervical surface. The periphery is preferably 40 microns Diamond grain coated. The pulpal and approximal surfaces are without diamond covering. The embodiment can be used both in the mesial and in the distal box large, conventionally prepared cavities can be used.

The adapter shaft of the tools according to the invention transmits the vibration of the handpiece on the processing block. The adapter shaft can be used with a Vibration characteristics are provided by which to be transmitted Vibration of the handpiece is changed. By choosing a suitable one Vibration characteristics of the adapter shaft, it is therefore possible to move adapt the processing block to the respective task. Several different adapter shafts can be made available for different tasks will. The adapter shaft acts not only as a coupling link between Handpiece and processing block, but as a vibration transformer with which an optimal movement of the processing block can be set. The Angling the adapter shaft can be chosen so that the fiction tools especially in the mesial or distal approximal box for use can come. With a special mesial adapter shaft, all me sial areas of all four quadrants can be reached. Accordingly, with one special distal approach, all distal surfaces of all four quadrants can be reached.

The tools according to the invention can be made from all medically harmless Materials are produced that are suitable for cavity processing Have properties. Metals and metal alloys in particular come in handy this purpose in question. The use of plastics is also conceivable.

Sonic or ultrasonic dental handpieces can be used as the drive unit. The Sound or. Ultrasonic vibration should be such that all work surfaces of the instrument can work optimally. For most applications Elliptical or circular vibrations are more suitable than one-dimensional ones  Vibrations. In this case, an oscillation amplitude of preferably less chosen as 0.2 mm. An example of a sonic handpiece that is an elliptical Provides vibration, is the SonicFlex Lux 2000L (KaVo GmbH, Biberach, D), the performs an elliptical swinging motion with a frequency of 65 kHz. The Vibration amplitude can be reduced with this device via the air pressure, which allows a finishing mode. An example of a sonic handpiece that The Odontoson-M ultrasound device (company A / S L. Goof, Denmark). Due to the special kinematics of an elliptical or circular vibration is the simultaneous, three-dimensional processing All cavity walls of the approximal box possible.

As restoration material for the tools according to the invention prepared cavities are suitable for all conventional restoration materials. Composite is currently favored for this purpose. But it is also conceivable that advanced compomers are used. It is also possible to post the cavity preparation with the tool according to the invention has a congruent, prefabricated fitting body made of ceramic, composite, ormocer or other To cement dental materials into the cavity.

In addition to water, liquids are also suitable as cooling medium, the abrasives and / or caries contrast agents and / or disinfectant and / or mineralizing Additives included.

For working with the diamond-coated approaches, a modified, Simplified cavity processing technology developed. First in the Sidebar with a spherical diamond access to the approximal Caries lesion created. The remaining transverse enamel lamella is marked with a Hand instrument removed. Instead of the otherwise usual caries removal is now the newly developed approach is applied to the occlusal opening of the lesion and at inserted into the cavity at full pressure with slight pressure. The instrument paves the way the right way by itself, active guidance is not necessary. After some short vertical saw movements with reduced power are the  Preparation and finishing of the cavity edges finished. Next is that Excavating the dentine caries with slowly rotating rose burs, preferably using cold light and magnifying glasses. If necessary, will be completed Caries removal again briefly with the tool according to the invention reworked.

Fifteen extracted, human maxillary molars of the same size selected, which from Time of extraction up to the start of the experiment in 0.1% thymol solution had been stored. First, their tooth roots were scanned by Remains of desmodone. After cleaning the crowns with a pumice stone powder-water mixture on rotating brushes they were with a cold poly merizing plastic (Paladur, Kulzer GmbH, Wehrheim, D) on special Sample carrier embedded.

In the control group there were ten randomly selected test teeth in five Box-shaped, conventional mesial (M-) or distal (D-) cavities prepared. The oro-facial width was 3.0 mm, the mesio-distal depth was 2.2 mm and the Height was 3.5 mm. The rough preparation was done with rotating 80 µm diamond grind in the red contra-angle (Micro Mega SA, Geneve-Acacias, CH) under water spray cooling. Under the stereo microscope (M5A, Wild-Leitz AG, Heerbrugg, CH) was then cleaned with rotating 25 µm diamond grinders (Universal Prep-Set, Intensive SA, Lugano, CH) damp finished. The time required for processing was not logged.

Five M and D cavities each from the Cavishape group (Intensive SA, Lugano, CH), or of the group with the newly developed approaches were randomly selected for the The remaining ten teeth distributed that each group represented both groups were. To simulate the approximal caries, mesial and distal spherical diamond grinder standardized under constant water cooling, spherical "approximal lesions" prepared. After that, the test teeth were in one Dentiform used, which simulated the neighboring tooth conditions in the dental arch.  

In the Cavisha group, the "approximal lesions" were rotated Diamonds (Piccolo preparation set, Intensiv SA, Lugano, CH) in the red contra-angle (Micro Mega SA, Geneve-Acacias, CH) under water spray cooling from an occlusal perspective opened. The remaining transverse melting bar was made with a hand instrument removed. After the neighboring tooth with a metal matrix (Hawe matrix band Sigveland 0.05 mm, Hawe Neos Dental, Gentillino, CH) had been protected, the occlusal area as well as the cervical step were covered with a pear-shaped 15 µm diamonds (Picolo Set, Intensiv SA) finished. Next were the axial ones Edges, as well as the axio-cervical curvatures with a flexible file (Cavishape 25 µm) in the EVA contra-angle handpiece with fixable head and 0.4 mm stroke (KaVo GmbH, Biberach, D) processed under water spray cooling. The time from the start of the Finishing diamonds were recorded until the cavity was completed.

In the group of tools according to the invention was one machining block worked, which in the frontal view resembled a cuboid with a semicircular base. The horizontal section corresponded to an isosceles trapezoid. It was according to the modified cavity processing technology. The timing was done from attaching the instrument to the transversal melting bar to finished position of the cavity.

The cavities were used for the investigation of the cavity edge morphology a thin-flowing, addition-curing silicone impression compound (President light body, Coltene AG, Altstätten, CH) replicated. The replicas were made 24 hours later under vacuum with epoxy resin (Stycast 1266, Emerson & Cuming Europe, Westerlo- Oevel, B) poured out. The quantitative marginal analysis was carried out on gold vaporized (Balzers SCD 030, Balzers Union AG, Balzers, FL) positive epoxy resin computer-assisted at 200x magnification in a scanning electron microscope (Amray 1810 / T, Amray Inc., Bedford, MA, USA), whereby after the fracture-free preparation margin, Melting edge chipping <50 µm and melting edge chipping <50 µm was distinguished.  

Table I shows the percentages of the fracture-free margin. For the total approximal marginal length (total) could not make any significant differences can be found between the three methods (Kruskall-Wallis; p <0.05). Also on no significant differences were found in the axial peripheral regions (Kruskall-Wallis; p <0.05). In contrast, the Cavishape instruments cut in cervical edge area significantly compared to the rotating diamonds (Kruskal- Wallis, Mann-Whitney; p <0.05) and compared to the instruments according to the invention were highly significant (Kruskal-Wallis, Mann-Whitney; p <0.001) worse. The destructive potential of Cavisha approaches at the cervical level was also reflected in the high values of enamel chipping (Tab. II), the larger defects (<50 µm) being particularly impressive. Next The percentage distribution also became the absolute number of the melt split recordings. The corresponding values can be found in Table III men.

The times required for processing the cavities are in Table IV listed. It became clear that the tools according to the invention were significant allowed shorter processing times than the Cavishape instruments (unpaired ter t test; p <0.001).

Using the example of an approximal cavity, the one with sound-operated instruments was used generated edge quality with the help of quantitative scanning electron optical Edge analysis compared to rotating diamonds or flexible diamond-coated ones Files examined. In addition, the one needed for preparation and finishing Time determined.

The tools according to the invention were 86.8 + in the cervical marginal area 12.5% of "fracture-free edge course" signifi the other two processes edge (p <0.05). Axial were between 86.1 + 9.8 and 94.2 + 5.2% found no significant differences between the three methods posed.  

The total time required for cavity preparation and finishing was over the sound-operated tools with 75.5 + 0.2 s significantly (p <0.05) shorter, than with the flexible files with 137.2 + 26.5 s. Since the invention Tools in addition to their non-destructiveness and their speed also easy are handled, they appear among many other tasks, especially for the processing of small approximal cavities as the instruments of choice.

Table 1

Percentages of fracture-free cavity margin (n = 10; average value + SD). Total = total approximal cavity margin; axial = axial cavity walls; cervical = cervical cavity level

Table II

a) Percentage of chip edge chipping <50 µm of the cavity edge length in percent (n = 10; average value ± SD). Total = total approximal cavity margin; axial = axial cavity walls; cervical = cervical cavity level

b) Percentage of chip edge chipping <50 µm of the cavity edge length in percent (n = 10; average value ± SD). Total = total approximal cavity margin; axial = axial cavity walls; cervical = cervical cavity level

Table III

Absolute number of enamel edge chips (n = 10; average value ± SD): <50 µm / <50 µm. Total = total approximal cavity margin; axial = axial cavity walls; cervical = cervical cavity level

Table IV

Time required in seconds for the newly developed instruments and for the Cavishape process

Claims (7)

1. A tool for machining tooth cavities, which can be driven by a sonic or ultrasonic dental handpiece, characterized by a machining block ( 1 , 21 , 41 , 51 ) which is connected or detachably connectable to an adapter shaft ( 2 , 22 , 42 , 52 ), whose working surfaces facing the inner surfaces of the cavity are covered with abrading material, and whose shape is adapted to the shape of the cavity in such a way that several to all differently oriented inner surfaces of the cavity can be machined simultaneously. 2. Tool according to claim 1, characterized in that the machining block ( 1 , 21 , 41 , 51 ) on a surface facing a neighboring tooth is not abrading. 3. Tool according to claim 1 or 2, characterized in that the adapter shaft ( 2 , 22 , 42 , 52 ) has an inner channel ( 3 , 43 ) and an outlet opening for coolant. 4. Tool according to one of claims 1 to 3, characterized in that at least one working surface of the machining block ( 1 , 21 , 41 , 51 ) is at an angle to the longitudinal axis of the handpiece. 5. Tool according to one of claims 1 to 4, characterized in that at least one work surface with natural or artificial diamond grain or cubic boron carbide is occupied. 6. Tool according to one of claims 1 to 5, characterized in that the releasably with the machining block ( 1 , 21 , 41 , 51 ) connected adapter shaft at its block-side end is formed as a longitudinally slotted tube end ( 42 '), the with a terminal bead or fold ( 48 ) engages in a transverse slot ( 49 ) which cuts a longitudinal channel ( 43 ) in the processing block ( 1 , 21 , 41 , 51 ) for the insertion of the pipe end ( 42 ') of the adapter shaft ( 42 ). 7. adapter shaft for a tool according to one of claims 1 to 6.