DENTAL CONTRA-ANGLE, INTENDED FOR TREATING HARD MATERIALS IN A PATIENT'S ORAL CAVITY

Abstract

DENTAL CONTRA-ANGLE FOR PROCESSING HARD MATERIALS IN THE ORAL CAVITY OF A PATIENT Dental contra-angle (1) for processing hard materials in the oral cavity of a patient, comprising an outer sleeve (2) provided with a gripping portion (2A) extending along a longitudinal axis (3) and a head portion (2B) extending along an axis of rotation (4), a collet (5) for holding a processing tool for processing hard materials, the collet (5) being housed in the head portion (2B) rotatably about the axis of rotation (4) by a first and a second rolling bearing (6, 7) and a coupling device (8) on the gripping portion (2A) for connecting the dental contra-angle (1) with a power and / or control device,the transmission ratio of the rotation speed of the dental contra-angle (1) being 1:4 ± 3% and the clamping collet (5) having an extraction force greater than 35N according to ISO 14457:2017.,

Description

Title of the invention: DENTAL CONTRA-ANGLE, INTENDED FOR TREATING HARD MATERIALS IN THE ORAL CAVITY OF A PATIENT

[0001] The present invention relates to a dental contra-angle, which is designed to be capable of treating hard material in the oral cavity of a patient.

[0002] Artificial dental crowns and dental prostheses, for example dental bridges, are made of different materials. In recent years, zirconia material has been used more and more frequently for this purpose. This is due, among other things, to the fact that zirconia is free of allergens, its color is very close to the natural color of teeth, and its increased hardness offers significant advantages, especially for dental prostheses that replace several teeth. But it is precisely this increased hardness that represents a real challenge for dentists, especially when it comes to treatment, for example, to extract a dental crown or a zirconia dental prosthesis present in the oral cavity of a patient. Currently, this operation is carried out using conventional contra-angles, which are, however, dedicated to the treatment of softer materials, for example natural dental tissue or caries.The use of contra-angles of this type for the treatment of hard materials, especially zirconia, but also other ceramics or particularly hard metal alloys in the oral cavity of a patient results in either very long treatment times / or rapid wear or even breakage of parts of the contra-angles which are particularly stressed when treating hard materials.

[0003] Therefore, the aim of the present invention is to design a dental contra-angle so that it is particularly suitable for treating hard materials in the oral cavity of a patient. The dental contra-angle must be designed in particular so as to better withstand high forces generated during the treatment of hard materials in the oral cavity of a patient both by the hard material itself and also by the user of the dental contra-angle.

[0004] This object is achieved according to the present invention by a dental contra-angle intended to treat hard materials in the oral cavity of a patient which comprises an outer sleeve delimiting the dental contra-angle with respect to the environment, provided with a gripping part which extends along a longitudinal axis and a head part which extends along an axis of rotation, the longitudinal axis and the axis of rotation being placed with respect to each other at an angle other than 0°, a clamp, for holding a treatment tool intended to treat hard materials, the collet being mounted in the head part rotatably about the axis of rotation by a first and a second rolling bearing and a coupling device on the gripping part, for connecting the dental contra-angle with a supply and / or control device. According to the invention, the transmission ratio of the rotational speed of the dental contra-angle is 1:4 ± 3% and the collet exhibits an extraction force of more than 35N according to ISO 14457:2017. Particularly advantageous embodiments are described.

[0005] In one embodiment of the contra-angle, the first and second rolling bearings are each housed on a first and second rolling seat, the first and second rolling seats being provided on the same rolling body of the head portion.

[0006] In one embodiment of the contra-angle, an angular gear is placed in the gripping portion.

[0007]

[0008] In one embodiment of the contra-angle, a first toothed wheel of the angular gear projects into an orifice in a bearing bush, in which a second toothed wheel of the angular gear is placed such that the first toothed wheel and the second toothed wheel mesh with each other.

[0009] In one embodiment of the contra-angle, the clamping collet is designed as a force-compliance clamping collet, provided with several spring arms designed elastically relative to the axis of rotation.

[0010] In one embodiment of the contra-angle, the collet comprises a tool receiving hole and a tool guide portion, the treatment tool being capable of being inserted into and removed from the dental contra-angle through the tool receiving hole, and in the tool guide portion a shank of the treatment tool being supported in a radial direction relative to the axis of rotation, the tool guide portion having an inner diameter of 1.6 mm and extending from the tool receiving hole with a length of at least 4.5 mm in the direction of the spring arms of the collet.

[0011] In one embodiment of the contra-angle, the tool guide portion extends to a portion of the collet which connects to the tool guide portion and whose inner diameter is other than 1.6 mm.

[0012] In one embodiment of the contra-angle, the clamping collet, including a keyed sleeve intended to detach the processing tool from the clamping collet, has a length of at least 12 mm.

[0013] In one embodiment of the contra-angle, the first and second rolling seats are designed by surfaces of the rolling body designed substantially parallel to the axis of rotation.

[0014] In one embodiment of the contra-angle, the rolling body is constituted by the internal face of the head part.

[0015] In one embodiment of the contra-angle, each of the first and second rolling bearings has an outer raceway having a peripheral surface which is housed on the first and second rolling seats.

[0016] In one embodiment of the contra-angle, at least the first or second rolling bearing comprises at least nine rolling elements.

[0017] In one embodiment of the contra-angle, at least the first or second rolling bearing is designed as a shoulder bearing.

[0018] In one embodiment of the contra-angle, a push button is provided on the head portion, intended to detach the treatment tool from the collet, the push button having an outside diameter of at least 9.0 mm.

[0019] In one embodiment of the contra-angle, for differentiation from the dental contra-angle, the push button has a marking.

[0020] In one embodiment of the contra-angle, at most three orifices are placed in a circle around the tool housing orifice, for the distribution of a cooling agent.

[0021] In one embodiment of the contra-angle, a light emitting device is placed on or adjacent to the head portion for distributing light to the treatment tool and / or the treatment site.

[0022] The dental contra-angle according to the invention, intended for treating hard materials in the oral cavity of a patient, comprises an outer sleeve, which delimits the dental contra-angle with respect to the environment and which comprises a gripping part, which extends along a longitudinal axis and a head part, which extends along an axis of rotation. The longitudinal axis and the axis of rotation are placed relative to each other at an angle other than 0°, so that a treatment tool intended for treating hard materials projects from the dental contra-angle by forming an elbow relative to the gripping part or the longitudinal axis.

[0023] The dental contra-angle further comprises a clamping collet, for holding the treatment tool intended for treating hard materials, the clamping collet being housed in the head part in a rotatable manner about the axis of rotation by a first and a second rolling bearing, as well as a coupling device on the gripping part, intended to connect the dental contra-angle with a power supply and / or control device and / or with a motor drive device.

[0024] The rotation speed transmission ratio of the dental contra-angle according to the invention is 1:4 ± 3%. For example, the maximum input rotation speed (which clearly depends on the drive motor provided on the dental contra-angle) is 40,000 rpm and the maximum output speed is consequently 160,000 rpm. The rotation speed transmission ratio of 1:4 ± 3% thus provides a low maximum rotation speed, compared to other contra-angles intended for restoration and prosthetics, which has the effect of reducing the wear phenomenon of the rotating structural elements of the dental contra-angle.The reduced wear counterbalances the high stress on the rotating structural elements of the dental contra-angle when processing hard materials in the oral cavity, thus the rotation speed transmission ratio of 1:4 ± 3% increases the service life of the dental contra-angle, despite the higher stresses experienced when processing hard materials.

[0025] The clamp of the dental contra-angle according to the invention exhibits an extraction force of more than 35N, preferably more than 36N, according to ISO 14457:2017. The extraction force is therefore increased, in comparison with other contra-angles intended for restoration and prosthetics. The increased extraction force means that the clamp holds the treatment tool (rotary instrument) with a higher force, i.e. the clamping force of the clamp is increased. The extraction force or the clamping force is estimated to be preferably about 20% higher in comparison with other contra-angles intended for restoration and prosthetics.The higher extraction force or clamping force is due, for example, to a higher wall thickness of at least parts of the collet and / or to an enlargement of the collet, for example, its elongation in comparison with other contra-angles intended for restoration and prosthetics, and / or to specific geometrical characteristics of at least parts of the collet. Advantageously, the increased extraction force or clamping force has the effect that the collet can reliably hold the treatment tool, despite the high mechanical stress experienced when treating hard materials in the oral cavity of a patient.

[0026] The first and second rolling bearings of the dental contra-angle according to the invention are each preferably housed on a first and a second rolling seat, the first and second rolling seats being provided on the same rolling body of the head part. This feature has the effect of increasing in particular the mechanical stability of the dental contra-angle, which in comparison with other contra-angles intended for restoration and prosthetics, allows it to better withstand the stresses undergone during the treatment of hard materials in the oral cavity of a patient. The rolling body is preferably designed in a single holding, for example in the form of a bearing shell designed inside the head part or by the inner face of the head part of the outer sleeve. The rolling body may, however, also consist of several parts which are connected to each other so as to form a single structural element, from the operational point of view and / or to act operationally as a structural element designed in one piece.

[0027] Thus, each individual feature mentioned above advantageously increases the suitability of the dental contra-angle handpiece according to the invention for processing hard materials, in particular zirconia in the oral cavity of a patient. The combination of several or even all of said features which advantageously further increase the suitability of the dental contra-angle handpiece according to the invention for processing hard materials, also through synergistic effects, is however particularly advantageous. Thus, for example, the transmission ratio of the rotational speed of 1:4 ± 3% not only reduces the stress on the drive train, it also reduces the stress on the collet, in addition to the previously described adapted geometry or modified dimensions of the collet.In accordance with the above, providing the first and second bearing seats on the same rolling body for the collet chuck also has advantages, since the pressing force exerted by the user on the hard material to be processed is transferred from the collet chuck to the rolling bearings and the rolling body and can be absorbed by it, thereby unloading the collet chuck.

[0028] The invention is explained below with the aid of preferred embodiment examples and with reference to the attached drawings. The figures represent

[0029] [Fig.l] [Fig.l]: A side exterior view of a dental contra-angle for treating hard materials in a patient's oral cavity;

[0030] [Fig.2] [Fig.2]: an elevation view of the dental contra-angle of [Fig.l];

[0031] [Fig.3] [Fig.3]: a partial section of a dental contra-angle intended for treating hard materials in a patient's oral cavity.

[0032] The dental contra-angle 1 intended for treating hard materials, in particular zirconia in the oral cavity of a patient shown in Figures 1 to 3 comprises an outer sleeve 2 delimiting the dental contra-angle 1 with respect to the environment, provided with a gripping part 2A, which extends along a longitudinal axis 3 and a head part 2B, which extends along an axis of rotation 4. The longitudinal axis 3 and the axis of rotation 4 are placed with respect to each other at an angle different from 0°, so that a treatment tool (not shown) intended for treating hard materials projects from the dental contra-angle 1 by forming an elbow with respect to the gripping part 2A or with respect to the longitudinal axis 3.

[0033] In the head part 2B is provided a clamping collet 5, ensuring the holding of the treatment tool intended for treating hard materials. The clamping collet 5 is housed in the head part 2B rotatably about the axis of rotation 4 by a first and a second rolling bearing 6, 7, in particular ball bearings. The clamping collet 5 exhibits an extraction force or a clamping force for the treatment tool of more than 35N according to ISO 14457:2017, which ensures reliable fixation of the treatment tool also when treating hard materials in the oral cavity of a patient.

[0034] The clamping pliers 5 are preferably designed as force-fitting or friction-fitting clamps with a plurality of spring arms 17 designed elastically relative to the rotation axis 4. Advantageously, the force-fitting clamping pliers 5 are capable of providing sufficient clamping force to hold the tool for treating a hard material in the oral cavity of a patient.

[0035] The clamping pliers 5 further comprises a tool receiving opening 18 and a tool guide portion 5A. Through the tool receiving opening 18, the treatment tool can be inserted into and removed from the clamping pliers 5 and the dental contra-angle 1. In the tool guide portion 5A, a shank of the treatment tool is supported in a radial direction relative to the axis of rotation 4, in particular if during the treatment of a hard material in the oral cavity of a patient, radial forces (relative to the axis of rotation 4) act on the treatment tool. The tool guide portion 5A preferably has an inner diameter of 1.6 mm so that, when inserted into the collet 5, the shank of the processing tool contacts the inner wall or is at least separated therefrom by only a minimal air gap.The tool guide portion 5A extends in particular from the tool receiving opening 18 with a length of at least 4.5 mm, preferably at least 5.0 mm in the direction of the spring arm 17 of the collet 5. The length of the tool guide portion 5A of at least 4.5 mm, increased in comparison with other contra-angles for restoration and prosthetics, and the inner diameter of 1.6 mm thus reliably support the processing tool on a longer tool shank portion when processing hard material, which advantageously ensures increased mechanical stability, as required for processing hard material.

[0036] The tool guide portion 5A extends with a length of at least 4.5 mm from the tool housing hole 18, in particular to a portion 5B of the collet 5 which connects to the tool guide portion 5A, the inner diameter of which is different from 1.6 mm. The connected portion 5B of the collet 5 comprises, for example, a clamping portion of the collet 5 and / or the spring arms 17 of the collet chuck 5 and / or a part of the collet chuck 5 with a further inner diameter, greater than 1.6 mm and / or a part of the collet chuck 5 with a further inner diameter, less than 1.6 mm. The tool guide part 5A is arranged in particular between the tool receiving hole 18 and the spring arms 17 of the collet chuck 5. The tool guide part 5A is provided in particular in the area of the second rolling bearing 7 which is arranged closer to the tool receiving hole 18, so that advantageously, forces acting on the treatment tool can be directly transmitted via the second rolling bearing to the head part 2B of the dental contra-angle 1.

[0037] Preferably, the collet 5 has, by including a keyed sleeve 19 for detaching the processing tool from the collet 5, a length or total length of at least 12 mm. Thus, the total length of at least 12 mm of the collet 5, increased in comparison with other contra-angles intended for restoration and prosthetics, reliably supports the processing tool over a larger part of the tool shank when processing hard material and advantageously ensures increased mechanical stability, as required for processing hard material.

[0038] The first and second rolling bearings or ball bearings 6, 7, which rotatably accommodate the collet 5 in the head part 2B, are each accommodated on a first and a second rolling seat 10, 11, the first and second rolling seats 10, 11 being provided on the same rolling body 9 of the head part 2B. Since both rolling seats 10, 11 and thus in particular also both rolling bearings 6, 7 are provided on the same rolling body 9, the dental contra-angle handpiece 1 exhibits increased mechanical robustness (in comparison with other contra-angle handpieces for restoration and prosthetics, on which the rolling seats are provided on two different rolling bodies), such as is required for the treatment of hard material in the oral cavity of a patient.

[0039] The first and second rolling bearing seats 10, 11 are designed by surfaces 20 of the rolling body 9 designed substantially parallel to the axis of rotation 4. Preferably, the rolling body 9 is constituted by the head part 2B and / or the surfaces 20 are constituted by the inner face of the head part 2B of the outer sleeve 2. Thus, no additional rolling body is advantageously necessary to constitute the rolling bearing seats 10, 11 and / or to accommodate the rolling bearings 6, 7. It goes without saying that it is possible as a variant for the rolling body 9 to be designed with the rolling bearing seats 10, 11 as a separate structural element, placed in the head part 2B, for example in the form of a bearing shell.

[0040] The rolling bearings 6, 7 preferably each comprise an outer, substantially cylindrical raceway provided with an enveloping surface or outer peripheral surface 21, 22. Preferably, each time a peripheral surface 21, 22 of an outer raceway of the first and second rolling bearing 6, 7 is housed in a rotationally fixed manner on the first and second rolling bearing seats 10, 11.

[0041] Preferably, at least the first and / or second rolling bearing 6, 7 comprises ceramic components. In particular, the rolling elements of the first and / or second rolling bearing 6, 7 are made of a ceramic material.

[0042] Preferably, at least the first and / or second rolling bearing 6, 7 comprises at least nine rolling elements. This, in comparison with other contra-angles intended for restoration and prosthetics, is a higher number of rolling elements. Thus, the forces which during the treatment of a hard material in the oral cavity of a patient act on the treatment tool and the dental contra-angle 1 are advantageously distributed over a larger number of rolling elements, which gives increased robustness to the rolling bearings 6, 7 and the dental contra-angle 1 which are better suited to the treatment of a hard material in the oral cavity of a patient. The rolling elements preferably have a diameter of approximately 1 mm.

[0043] Preferably, at least the first and / or second rolling bearing 6, 7 is designed as a shoulder bearing. Advantageously, the rolling bearings 6, 7 designed as shoulder bearings are particularly suitable for absorbing forces which, during the treatment of a hard material in the oral cavity of a patient, act on the treatment tool and on the dental contra-angle 1.

[0044] On the end of the gripping part 2A which is remote from the head part 2B, a coupling device 8 is provided, intended to connect the dental contra-angle 1 with a power supply and / or control device and / or with a drive device, in particular with an electric motor. The drive device can either be integrated in the outer sleeve 2 of the dental contra-angle 1, or as a separate component, be capable of being removably connected via the coupling device 8 with the dental contra-angle 1.

[0045] In the gripping part 2A, in particular in the area of a curvature of the gripping part 2A, an angular gear 12 is provided. For this purpose, a driven shaft 26 carries a first gear wheel or pinion 13 and a driving shaft 27 carries a second gear wheel 16. The first and second gear wheels 13, 16 mesh with each other and constitute the angular gear 12 constituted as a first transmission gear. In or on the head part 2B, an additional angular gear 28 is provided. It comprises a third gear wheel 29 on the driven shaft 26 and a toothing 30, connected in a rotationally fixed manner with the collet 5 which mesh with each other and constitute the angular gear 28 constituted as a second transmission gear. Thus, the angular gear 28 is designed to transmit the driving movement and the torque to the collet chuck 5. Due to the number of their teeth, the two angular gears 12 and 28 are, for example, designed and interact in such a way that the transmission ratio of the rotational speed of the dental contra-angle (1) amounts to 1:4 ± 3%. This transmission ratio of the rotational speed of 1:4 ± 3% has proven to be particularly suitable for the treatment of hard materials in the oral cavity of a patient, both in terms of the torque with which the hard material is treated, the duration of the treatment of the hard material and the wear of the particularly stressed components of the dental contra-angle 1.

[0046] The two shafts 26, 27 are rotatably housed by means of rolling bearings in rolling bearing bushes 15 and 31. The rolling bearing bushes 15, 31 advantageously also serve to protect the gears 12, 28 and the rolling bearings against the penetration of particles of the hard material being treated. In order for the first output gear 13 and the second input gear 16 to mesh with each other despite being enclosed by the rolling bearing bushes 15, 31, an orifice 14 is provided in the bearing bush 15 in which the second gear 16 is received, through which the first gear 13 projects. To ensure its sealing, the orifice 14 is surrounded by a sealing element, for example an O-ring.

[0047] Preferably, a push button 23 is provided on the head part 2B, intended to detach the processing tool from the clamping collet 5. The push button 23 is placed in particular on the end of the head part 2B which is opposite the tool housing orifice 18. The push button 23 is designed so as to be movable relative to the outer sleeve 2, in particular to the head part 2B. The push button 23 is movable in particular in a known manner in the direction of the tool receiving opening 18, whereupon the key sleeve 19 also moves in the direction of the tool receiving opening 18 and the wedge-shaped extension of the key sleeve 19 engages in the spring arms 17 of the clamping sleeve 5 and moves them away from each other in the radial direction, so that the processing tool can be inserted into the clamping sleeve 5 or released therefrom.

[0048] The push button 23 preferably has an outer diameter of at least 9.0 mm. This advantageously facilitates the freedom of manipulation of the push button 23, in particular also with regard to the extraction force or the previously mentioned clamping force of the clamping sleeve 5.

[0049] To differentiate the dental contra-angle 1 from other dental contra-angles, in particular other dental contra-angles intended for restoration and prosthetics, the push button 23 has a marking. The marking on the button push button 23 preferably comprises a color and / or alphanumeric marking or a symbol. Particularly preferably, a color marking of a circular round shape or a circular surface, black in color, for example, is provided on the push button 23, see [Fig. 2]. To differentiate them, the dental contra-angles have a colored ring made of plastic on their end, near the coupling device 8. The marking provided on the push button 23 further facilitates and makes it safer to identify and differentiate the dental contra-angle 1 intended for treating hard materials in the oral cavity of a patient, which further advantageously reduces the probability of incorrect use of the dental contra-angle 1 intended for treating hard materials.

[0050] The dental contra-angle 1 preferably comprises a maximum of three orifices 24 placed in a circle around the tool housing orifice 18, for dispensing a cooling agent, in particular an air / water spray. This feature also advantageously increases the robustness of the dental contra-angle 1 in comparison with other dental contra-angles intended for restoration and prosthetics which are provided with more than three orifices 24 for dispensing cooling agent.

[0051] A light-emitting device 25 for emitting light onto the treatment tool and / or onto the area to be treated is preferably provided on the dental contra-angle 1, in particular on the head portion 2B or is adjacent thereto. This advantageously improves the visibility of a hard material to be treated for the user. The light-emitting device 25 comprises, for example, a glass or plastic light conductor and / or a light source, in particular a light-emitting diode (LED).

[0052] The exemplary embodiments described or represented serve in particular to illustrate the invention. Thus, the characteristics disclosed in an exemplary embodiment are not restricted to said exemplary embodiment, but may be associated individually or jointly with one or more characteristics of the other exemplary embodiments.

Claims

Claims

1. Dental contra-angle handpiece (1), intended for treating hard materials in the oral cavity of a patient, comprising an outer sleeve (2) delimiting the dental contra-angle handpiece (1) with respect to the environment, provided with a gripping part (2A) which extends along a longitudinal axis (3) and a head part (2B) which extends along an axis of rotation (4), the longitudinal axis (3) and the axis of rotation (4) being placed relative to each other at an angle other than 0°, a collet (5), for holding a treatment tool intended for treating hard materials, the collet (5) being housed in the head part (2B) rotatably about the axis of rotation (4) by a first and a second rolling bearing (6, 7) and a coupling device (8) on the gripping part (2A), intended to connect the dental contra-angle (1) with a power supply and / or control device,characterized in that the transmission ratio of the rotation speed of the dental contra-angle (1) is 1:4 ± 3% and in that the clamping collet (5) exhibits an extraction force of more than 35N according to ISO 14457:2017.,

2. Dental contra-angle (1) according to claim 1, characterized in that the first and second rolling bearings (6, 7) are each housed on a first and second rolling seat (10, 11), the first and second rolling seat (10, 11) being provided on the same rolling body (9) of the head part (2B).

3. Dental contra-angle (1) according to any one of the preceding claims, characterized by an angular gear (12) placed in the gripping part (2A).

4. Dental contra-angle (1) according to claim 3, characterized in that a first toothed wheel (13) of the angular gear (12) projects into an orifice (14) in a bearing bush (15), in which a second toothed wheel (16) of the angular gear (12) is placed such that the first toothed wheel (13) and the second toothed wheel (16) mesh with each other.

5. Dental contra-angle handpiece (1) according to any one of the preceding claims, characterized in that the clamping pliers (5) are designed as force-fitting clamping pliers, provided with several spring arms (17) designed elastically relative to the rotation axis (4).

6. Dental contra-angle handpiece (1) according to claim 5, characterized in that the collet (5) has a tool receiving hole (18) and a tool guide portion (5A), the treatment tool being capable of being inserted into and removed from the dental contra-angle handpiece (1) through the tool receiving hole (18), and in the tool guide portion (5A) a shank of the treatment tool being supported in a radial direction relative to the rotation axis (4), the tool guide portion (5A) having an inner diameter of 1.6 mm and extending from the tool receiving hole (18) with a length of at least 4.5 mm in the direction of the spring arms (17) of the collet (5).

7. Dental contra-angle (1) according to claim 6, characterized in that the tool guide portion (5A) extends to a portion (5B) of the clamping collet (5) which connects to the tool guide portion (5A) (5) and whose inner diameter is different from 1.6 mm.

8. Dental contra-angle (1) according to any one of the preceding claims, characterized in that the clamping collet (5) including a keyed sleeve (19) intended to detach the treatment tool from the clamping collet (5) has a length of at least 12 mm.

9. Dental contra-angle (1) according to any one of claims 2 to 8, characterized in that the first and second rolling seats (10, 11) are designed by surfaces (20) of the rolling body (9) designed substantially parallel to the axis of rotation (4).

10. Dental contra-angle (1) according to any one of claims 2 to 9, characterized in that the rolling body (9) is constituted by the internal face of the head part (2B).

11. Dental contra-angle (1) according to any one of claims 2 to 10, characterized in that each of the first and second rolling bearings (6, 7) have an outer raceway comprising a peripheral surface (21, 22) which is housed on the first and second rolling seats (10, 11).

12. Dental contra-angle (1) according to any one of claims 2 to 11, characterized in that at least the first or second rolling bearing (6, 7) comprises at least nine rolling elements.

13. Dental contra-angle (1) according to any one of claims 2 to 12, characterized in that at least the first or second rolling bearing (6, 7) is designed as a shoulder bearing.

14. Dental contra-angle (1) according to any one of the preceding claims, characterized by a push button (23) provided on the head part (2B), intended to detach the treatment tool from the clamping collet (5), the push button (23) having an outer diameter of at least 9.0 mm.

15. Dental contra-angle (1) according to claim 14, characterized in that for differentiation of the dental contra-angle (1), the push button (23) has a marking.

16. Dental contra-angle (1) according to any one of the preceding claims taken in combination with claim 6, characterized by at most three orifices (24) placed in a circle around the tool housing orifice (18), for the distribution of a cooling agent.

17. Dental contra-angle (1) according to any one of the preceding claims, characterized by a light emitting device (25) placed on the head part (2B) or adjacent thereto, for distributing light onto the treatment tool and / or the treatment site.

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