WO2000016713A1

WO2000016713A1 - Device for preparing a tooth to accommodate a crown

Info

Publication number: WO2000016713A1
Application number: PCT/EP1999/006943
Authority: WO
Inventors: Gerd Neuschäfer
Original assignee: Neuschaefer Gerd
Priority date: 1998-09-22
Filing date: 1999-09-20
Publication date: 2000-03-30
Also published as: EP1115346A1; DE19843385C1

Abstract

A device for preparing one or several teeth (1) to accommodate a crown, bridge, or the like comprises a positioner (4), a starting template, a calibrator and a profile grinder. The positioner (4) has a first non-circular connecting part (5) for twist-proof arrangement in the tooth (1) and a second non-circular connecting part (8) for twist-proof accommodation of the starting template. The starting template is provided in the form of a shaped body that can be shaped by profile-grinding. The calibrator has a pin for accommodating the positioner (4) with the starting template which is shaped into the template and the profile grinder. The profile grinder has a length-adjustable arm and a grinding spindle whose angle and length can be adjusted, a feeler for the side faces of the template whereby the angle and length of said feeler can be adjusted, and a limiting feeler for reproducing the lower edge of the crown. The positioner (4), the starting template and the arm of the profile grinder have central bores (10) which are identical in diameter for accommodating a pin or the pin pertaining to the inventive device.

Description

Device for preparing a tooth for receiving a crown

The invention relates to a device for preparing one or more teeth for receiving a crown, bridge or the like, using an impression model containing model teeth. For the restoration of defective teeth and tooth gaps in human teeth, it is known to use crowns and bridges, the crown being used in the restoration of a single tooth while a bridge extends over several teeth.

Up to now, the restoration of a tooth using a crown has been carried out as follows:

The dentist first prepares the tooth to be restored by grinding the tooth to a tooth stump. Material is removed to make room for the crown. Grinding the tooth into a tooth stump requires considerable skill and concentration. This work is carried out by Dentist performed in the patient's mouth, whereby the view is partially obstructed and reactions of the patient can reduce the quality of this preparation. The expenditure of time is also influenced by anatomical obstacles, for example neighboring teeth. After the tooth is prepared to the tooth stump, an impression is taken in the patient's mouth to create a negative shape that corresponds to the tooth stump. The impression is then cast in plaster in the laboratory, and a positive model is created, i.e. a model tooth made of plaster. A technical crown is made on this model tooth stump, which the dentist later places over the tooth stump with the interposition of a cement or other fastener. The accuracy that can be achieved with the previous procedure is limited. Rework in the patient's mouth is usually required. In particular, difficulties can arise in the area of the crown edge, that is, at the point where the crown is to connect closely to the natural tooth material.

The invention has for its object to provide a device of the type described in the introduction, which allows a large part of the work previously carried out in the patient's mouth to be shifted outside of the mouth in order to perform this work outside the mouth and with greater accuracy and without being influenced by to be able to carry out the patient.

According to the invention, this is achieved in a device of the type described in the introduction in that a positioning body, a raw die, a calibration device and a copying grinder are provided, that the positioning body has a first non-circular connecting part for non-rotatable arrangement in the tooth and a second non-circular connecting part for non-rotatably receiving the raw matrix has that the raw die is designed as a shaped body that can be deformed by copy milling, that the calibration device has an axis for receiving the position. kidney body with the raw die deformed into the die and the copy grinder that the copy grinder has a variable-length arm and an adjustable in length and angle grinding head, an adjustable in angle and length button for the side surfaces of the die and a limit sensor for the image of the lower edge of the crown, and that the positioning body, the raw die and the arm of the copy grinder have a diameter-matching central bore for receiving one or the axis.

The invention is based on the idea of initially grinding only a recess in the tooth to be restored that is suitable and dimensioned for receiving a positioning body. The side walls of the tooth remain unaffected at this time. The positioning body is inserted into the recess to prevent it from rotating. The positioning body is designed in such a way that it has a first non-circular connection part for the rotation-proof arrangement in the tooth and a second non-round connection part for the rotation-proof reception of a raw die. It is used to ensure that the angular position of the raw matrix relative to the tooth axis is always maintained, so that it can also be used at a later point in the treatment. Since the recess is usually ground as a cylindrical, largely round recess, the first non-circular connecting part can be provided with a flattening, which is then filled in the tooth with a plastic material which hardens and connects to the tooth while it is being connected to the positioning body. The positioning body can thus be removed from the recess at any time and reinserted in the same angular position. The positioning body has a through hole in the center, which is intended for receiving an axis.

After the indentation in the tooth is made in the mouth and the positioning body is inserted so that it cannot rotate, a Taken the impression, the positioning body remains in the impression or can be used in this. This creates a negative mold that can be poured out with plaster or another corresponding material, so that in this way a model tooth or several model teeth are created as a positive model that are available for work outside the patient's mouth. The particular advantage is that the model tooth can now be ground to the tooth stump without any interference from the patient. A model tooth stump is thus created from the model tooth, the shape of which can be transferred to a raw matrix, in particular by copy milling. The raw die is a largely cylindrical shaped body, for example made of plastic. The resulting matrix represents a positive model as well as the model tooth stump. The side wall of the model tooth stump is molded into the side wall of the raw matrix. The intended course of the crown edge, i.e. the transition between the technical crown and the tooth stump, is molded on the top of the matrix. These method steps are also carried out using the positioning body or a body of matching shape, so that the rotationally secure angular position is also guaranteed.

Finally, the device also includes a calibration device which is suitable for receiving an axis and the positioning body with the raw die deformed into the die and a copy grinder. The axis can be a separate axis with the same diameter as the axis that is assigned to the bore of the positioning body. But it is also possible to use the same axis. A copy grinder is set using the calibration device. The copy grinder has a button to scan the side wall of the die and a limit sensor to scan the top end wall of the die in accordance with the crown edge. The calibration device serves this To fix parts in the correct relative position to each other, namely relative to the tooth stump model. After the grinding head has been calibrated in this way, the positioning body, the axis, the matrix and the grinding head are inserted into the patient's mouth and the material of the tooth is removed in accordance with the shape of the matrix. The tooth stump in the patient's mouth is created from the natural tooth to be restored to match the model tooth stump. It goes without saying that the technical crown was created in parallel with the use of the model tooth stump, which is then finally placed and fixed on the natural tooth stump.

The new device is advantageous in many ways. Since the shaping of the model tooth stump takes place outside the patient's mouth without restricting the patient's influence, the achievable fit of the crown or bridge is much better than in the prior art. Incorrect preparations such as undercuts or divergences (in the case of bridges) result in loss of tooth substance that is irretrievable in situ. With the new method, tooth loss is reduced to the necessary minimum by abrasion, which comparatively improves the stability and biological resistance of the tooth stump. The design of the model crown margin by controlled preparation and then ultimately the crown margin on the natural tooth is possible more precisely and without restrictions. The crown or bridge gets a flush seat on the tooth stump. Marginal caries is minimized. The length of time the crown stays in the mouth is extended, reducing the patient's overall treatment costs over a longer period of time. When using the new device, it becomes possible to carry out more work outside the patient's mouth, which advantageously increases the precision and shortens the necessary working time. The stress in treating the patient becomes comparatively less for the patient and the practitioner. The positioning body can be designed in such a way that the first non-round connecting part and the second non-round connecting part of the positioning body are essentially provided as parts arranged one behind the other in the axial direction, the positioning body having a comparatively smaller diameter in the region of its second non-round connecting part. It is understood that the first connection part and the second connection part can be formed as a one-piece molded body. However, a split design is also possible in which these two parts can in turn be joined to one another in a rotationally secure manner. The two connecting parts of the positioning body can be designed as separate molded parts which can be connected to one another in an axial arrangement in only one relative position so as to be secured against rotation.

The raw die is designed as an essentially cylindrical molded body made of plastic. Other materials for the raw die are also conceivable. It only has to be a material that enables the production of a permanent shape by machining.

The calibration device has a holder for clamping an axis. This axis can be the axis that is already assigned to the positioning body. Another option is to use a different axis with the same diameter. The raw die must also have a corresponding hole. The calibration device can be designed to receive the positioning body with the axis and the die. However, it is also possible for the calibration device to have its own body, the shape of which corresponds to that of the positioning body, so that the die can be accommodated in the calibration device in a manner secured against rotation. The calibration device is otherwise used to adjust the grinding head to the individual conditions on the die. The variable-length arm of the copy grinder has a rotary bearing for placement on the axis, in the area of which the limit sensor is arranged in association with the end wall of the die facing away from the tooth. In the calibration device, the button and the limit sensor are set relative to the grinding head, as required by the die. After this setting has been secured, the grinding cup is removed from the calibration device and can now be used together with the positioning body and the axis in the patient's mouth to shape the natural tooth by shaping with the grinding head to the tooth stump, as is the case with this the model tooth stump or the matrix requires.

The variable-length arm of the copy grinder can be designed telescopically, with a return spring acting on the arm in the shortening direction being provided. The return spring is not absolutely necessary. However, it makes working in the patient's mouth easier. The natural tooth is ground down to the tooth stump by tapping the form on the die. In particular, the intended crown edge is precisely ground according to the shape of the one end face of the die. It is also possible to transfer a marking groove in the upper area of the tooth, which gives the dentist an indication of the position to which the upper part of the tooth has to be removed from the occlusal surface in order to make room for the technical crown. It is understood that the grinding head must be designed so that it can be handled in the patient's mouth. This may include a bracket which can be connected to the grinding head and which can be turned into different angular positions in order to enable or simplify handling.

The new device is further explained and described on the basis of a preferred exemplary embodiment. Show it: 1 is a side view of the natural tooth, partially in section, with the positioning body used,

2 is a plan view of the positioning body used in the occlusal surface of the natural tooth,

3 shows a sectional illustration of a model tooth stump with an inserted positioning body and an attached raw die,

4 shows a schematically illustrated copy milling device,

5 is a partially sectioned side view of the calibration device when adjusting a copy grinder,

Fig. 6 shows the use of the set copy grinder in the patient's mouth and

Fig. 7 shows the removed material of the natural tooth after finishing the copy grinding.

In Fig. 1, a natural tooth 1 of the patient in need of restoration is shown as it is present in the patient's mouth within the dentition. The tooth 1 has a chewing surface 2 into which a cylindrical recess 3 of limited depth is ground. The diameter of the recess 3 is adapted or matched to the diameter of a positioning body 4. The positioning body 4 has a first lower connecting part 5, which has a non-circular cross section, so that it can be connected to the tooth 1 in a manner secured against rotation. For this purpose, the connection part 5 has on one side a flattened portion 6 which can extend over the entire height of the connection part 5. In the case of a cylindrical recess 3, a space 7 is thus created, which is filled with a plastic material, for example a plastic, after inserting the positioning body 4 into the recess 3. This material hardens and connects to the tooth 1, while it does not make a connection to the positioning body 4.

The positioning body 4 has in its upper part a second connection part 8 which can be formed in one piece with the lower connection part 5. As can be seen in particular in FIG. 2, the upper connecting part 8 has a trapezoidal shape, is therefore also out of round and therefore defines an angular position secured against rotation about an axis 9. The positioning body 4 has a through bore 10 concentric with the axis 9. The bore 10 is designed and intended for receiving a physical axis 11, for example in the form of a cylinder section. In order to fix the axis 11 in the positioning body 4, a resiliently expandable locking ring 12 can be accommodated in its lower region. This circlip 12 is not absolutely necessary.

After the positioning body in the manner shown in FIGS. 1 and 2 is inserted in the recess 3 of the natural tooth 1 secured against rotation, in this position an impression is taken from the corresponding position of the patient's dentition, ie an impression mass, usually with With the help of a spoon, applied, which after removal and hardening produces a negative shape of the natural tooth 1 together with the positioning body 4 inserted. This impression is poured out with plaster or another shaping material, so that a model tooth is created outside the patient's mouth, on which work can be carried out easily and precisely. This model tooth is prepared into a model tooth stump 13, as shown in FIG. 3. This model tooth stump 13 has the desired shape into which the natural tooth 1 according to FIG. 1 or 7 is to be brought in order to open the technical crown. to be able to take. The model tooth stump 13 has side surfaces 14 all around the axis 9, which are known in the mouth in a manner similar to hitherto on ground tooth stumps. The side faces

14 of the model tooth stump 13 have a model crown edge 15, which is also provided all around the axis 9 and represents the transition at which the lower crown edge of the crown should ultimately merge into the natural material of the tooth 1. It is understood that the course of the model crown edge

15 is not cylindrical, but is more or less irregular. Finally, a marking groove 16 is also formed on the model tooth stump 13, which gives the dentist an indication of how far the material of the tooth 1 is to be removed from the occlusal surface 2 in order to make room for the crown. The relationships between the model crown edge 15 and the marking groove 16, including the course of the side surface 14, are thus also fixed on the model.

The model tooth stump 13 formed from the model tooth by grinding is clamped with the positioning body 4 and a raw die 17 and the axis 11 in the relative position shown in FIG. 3 as a unit in a copy milling device 18 (FIG. 4). At least one end face of the raw die 17 is designed in accordance with the shape of the second connection part 8 of the positioning body 4. The individual parts of this copy milling device 18 are not described and described in detail since each copy milling device 18 can be used per se with which it is possible to transfer the shape of a part to another part. In the present case, the shape of the model tooth stump 13 is transferred to the cylindrical raw matrix 17, so that a matrix 19 is formed from the raw matrix 17 (FIG. 3), the side walls of which reproduce the shape of the side surfaces 14 of the model tooth stump 13. The marking groove 16 is also molded into the die 19 as a marking line 20. The model crown edge 15 is transferred into the upper end face 21 of the die 19. The course of the model crown edge 15 is molded on the one hand as the die crown edge 42 and on the other hand as the edge 43 of the die 19 in the region of the upper end face 21.

After the die 19 has been created with its shape in this way, both parts are removed from the copy milling device 18. The material of the model tooth stump 13 above the marking groove 16 is removed, and the resultant body serves as a model for the manufacture of the technical crown, so that it is manufactured in accordance with the course of the side surfaces 14 and the course of the model crown edge 15 or the die crown edge 42 can.

5 shows a calibration device 22. The calibration device 22 has a foot-like holder 23, which merges into a column 24 at the top, or is designed and intended directly for receiving one or the axis 11. The positioning body 4 is secured against rotation on the column 24 or on the axis 11, it also being possible to use a replacement body which matches the surface of the positioning body 4 (FIG. 1), as shown in FIG. 5. The upper connection part 8 of the positioning body 4 receives the die 19. A copy grinder 25 is placed on the axis 11. The copy grinder 25 has a rotary bearing 26, with which it is rotatably received about the axis 11 in accordance with arrow 27. In addition, the pivot bearing 26 and thus the entire copy grinder 25 is guided according to the height of the double arrow 28. The movement is limited by a height-adjustable limiting ring 47 on the axis 11. The copy grinder 25 has a variable-length arm 29, which can be telescopic, following the rotary bearing 26. The arm 29 ends in a lockable angular bearing 30, about the axis 31 of which a grinding head 32 with a turbine 33 and a grinding tool 34 can be pivoted and locked. The grinding tool 34 can vary in length relative to the turbine 33 according to arrow 35 be guided and ascertainable. However, it is also sufficient if this length is specified. On the housing of the turbine 33, a button 36 in an adjusting device 37 according to arrow 38 is adjustable and adjustable in length. The button 36 can also be pivoted according to the double arrow 39 and can be fixed with the adjusting device 37. A limit sensor 40 is provided on the rotary bearing 26 and is adjustable according to the double arrow 41.

The setting of the copy grinder 25 using the calibration device 22 is carried out as follows:

The tip of the grinding tool 34 and the tip of the button 36 must be adjusted to each other so that they both lie on a cylinder jacket around the axis 9. Since this condition applies to the die crown edge 42 and the edge 43 of the die 19, the tip of the grinding tool 34 is initially set on the die crown edge 42 and the tip of the button 36 is simultaneously set on the upper edge 43 of the die 19 in the region of the upper end face 21. At the same time, the angular bearing 30 and the actuating device 37 are determined, so that the grinding head 32 can no longer change its angular position relative to the arm 29. So that the tips of the grinding tool 34 and the button 36 are immovably fixed to each other. The distance between these two parts corresponds to a distance on the circumference of the die 19, namely between the edge 43 and the die crown edge 42 at one point on the circumference. Then the copy grinder 25 is lowered with its rotary bearing 26 on the axis 11 so that the tip of the button 36 lies on the marking line 20. The limiting ring 47 is then released and lowered onto the pivot bearing 26 and fixed. The limiting ring 47 forms a stroke limitation for the rotary bearing 26 and thus for the grinding head 32 and in particular for the grinding tool 34. Then the grinding head 32 with the rotary bearing 26 is lowered on the axis 11 to such an extent that the button 36 strikes the die crown edge 42. In this position the limit sensor 40 is set according to arrow 41 so that its tip sits on the end face 21. In this set position, the copy grinder 25 including the axis 11 with the positioning body 4 and the die 19 can be removed. This unit will then continue to be used in this set position.

6 shows the application of the copy grinder 25 set in this way in the patient's mouth. The natural tooth 1 is ground to a tooth stump 44. For this purpose, the positioning body 4 is first inserted into the recess 3 of the natural tooth 1 so that it cannot rotate. The positioning body 4 is connected to the die 19 and the axis 11. The variable-length arm 29 can be moved in accordance with the double arrow 45, material being removed from the natural tooth 1 until the tooth stump 44 with its shape corresponding to the die 19 is formed, in any case below the marking line 20. The shape of the die crown edge 42 is also shown here Transfer tooth stump 44, as well as the marking line 20 itself. The button 36 is limited in its movement or scans the shape of the die 19 and transfers it to the tooth stump 44 in a true-to-shape manner. The grinding head 32 can be rotated accordingly according to arrow 27, so that tooth 1 is ground true to size over its circumference.

These relationships are shown again in detail in FIG. 7, the tooth 1 with its initial shape (FIG. 1) being indicated in boundary lines and the tooth stump 44 resulting therefrom being shown in dashed lines. After the shape of the die 19 has been shaped in this way into the shape of the tooth stump 44 and also the marking line 20 appears as a marking line 46 on the tooth stump 44, the copying grinder 25, the axis 11 and ultimately also the positioning body 4 are removed. The material on the tooth stump 44 above the Marking line 46 is removed so that the technical crown produced in parallel can then be placed in a known manner.

B E Z U G S Z E I C H E N L I S T E

1 - tooth 11 - axis

2 - chewing surface 12 - circlip

3 - recess 13 - model tooth stump

4 - positioning body 14 - side surface

5 - connecting part 15 - model crown edge

6 - flattening 16 - marking groove

7 - Room 17 - Raw die

8 - connecting part 18 - copy milling device

9 - axis 19 - die

10 - Hole 20 - Marking Line

21 - end face 31 - axis

22 - Calibration device 32 - Grinding head

23 - bracket 33 - turbine

24 - column 34 - grinding tool

25 - copy grinder 35 - arrow

26 - pivot bearing 36 - button

27 - arrow 37 - adjusting device

28 - double arrow 38 - arrow

29 - arm 39 - double arrow

30 - Angular bearing 40 - Limit sensor

41 - double arrow

42 - Matrix crown rim

43 - edge

44 - tooth stump

45 - double arrow

46 - marking line

47 - Perimeter ring

Claims

P AT ENTANSP RÜ CHE

1. Device for preparing one or more teeth (1) for receiving a crown, bridge or the like using an impression model containing model teeth, characterized in that a positioning body (4), a raw matrix (17), a calibration device (22) and a copy grinder (25) are provided that the positioning body (4) has a first non-circular connection part (5) for non-rotatable arrangement in the tooth (1) and a second non-circular connection part (8) for non-rotatably receiving the raw die (17), that the Raw die (17) is designed as a shaped body which can be deformed by copy milling, that the calibration device (22) has an axis (11) for receiving the positioning body (4) with the raw die (17) deformed into the die (19) and the copy grinder (25) that the copy grinder (25) has a variable-length arm (29) and an adjustable in length and angle grinding head (32), one in angle and in length adjustable button (36) for the side surfaces of the die (19) and a limit sensor (40) for mapping the lower crown edge, and that the positioning body (4), the raw die (17) and the arm (29) of the copy grinder (25 ) have a matching central bore (10) for receiving one or the axis (11).

2. Device according to claim 1, characterized in that the first non-circular connecting part (5) and the second non-circular connecting part (8) of the positioning body (4) are provided essentially as parts arranged one behind the other in the axial direction, and in that the positioning body (4) has a comparatively smaller diameter in the region of its second non-circular connecting part (8).

3. Apparatus according to claim 2, characterized in that the two connection parts (5, 8) of the positioning body (4) are designed as separate molded parts which can be connected to one another in an axial arrangement in a relative position in a rotationally secure manner.

4. The device according to claim 1, characterized in that the raw die (17) is designed as a substantially cylindrical molded body made of plastic.

5. The device according to claim 1, characterized in that the calibration device (22) has a holder (23) for clamping an axis (11).

6. The device according to claim 1, characterized in that the variable-length arm (29) of the copy grinder (25) has a rotary bearing (29) for mounting on the axis (11), in the region of which the limit sensor (40) in association with that Tooth-facing end wall (21) of the die (19) is arranged.

7. The device according to claim 1 or 6, characterized in that the variable-length arm (29) of the copy grinder (25) is telescopic, and that an arm (29) acting in the shortening direction is provided return spring.