EP1931278A2

EP1931278A2 - Method for recording dental models

Info

Publication number: EP1931278A2
Application number: EP06777069A
Authority: EP
Inventors: Dirk Freyer; Nils Hanssen; Erwin Keeve; Lutz Ritter; Gerhard ZÜNDORF
Original assignee: SICAT GmbH and Co KG
Current assignee: SICAT GmbH and Co KG
Priority date: 2005-08-26
Filing date: 2006-08-25
Publication date: 2008-06-18
Also published as: DE102005040740A1; US20090191509A1; WO2007022996A2; WO2007022996A3

Abstract

The invention relates to a method for planning a surgical intervention on a body part, in particular on a patient jaw consisting in defining a common reference system between a set of patient data which is recorded by means of a recording unit and represents said three-dimensional body part and a body part model to be registered, in holding the patient body part in a fixing device (3) during acquisition of the patient data, in placing the fixing device in a defined position with respect to the recording device, after recording the patient data, in placing a model (7) into a corresponding position in the fixing device (3) by means of a holder (8) which is positioned in a defined manner with respect to the fixing device, in fixing the model (7) to the holder (8) in said defined position and in carrying out the other planned steps on the model (7) fixed to the holder (8).

Description

Method for registering dental models

On the one hand, the present invention relates to a method for planning an operative procedure on a body part, in particular on the jaw, of a patient, wherein a common reference system is defined as part of a registration between a set of patient data, which are created with a tomographic recording device in particular, and the body part in its three-dimensionality, and a model of the body part, wherein the patient is held during the recording of the patient data with the body part in a fixing device, which is mounted in relation to the recording device in a defined position. The invention relates as it were a system for carrying out such a method. In addition, the invention relates to a method for generating and recording in chronological order with a recording device recorded patient data of a body part, in particular the jaw, a patient, wherein the patient is held during the recording of the patient data with the body part in a fixing device in a defined position in Related to the recording device is attached.

For the planning of surgical interventions, especially in the jaw area, image data is taken by the patient in the preoperative phase by means of computed tomography (CT), cone-beam technique or magnetic resonance imaging (NMR) in order to incorporate the created volume data sets in the computer-aided planning of the later operations. However, the interpretation and use of patient data is often hampered by metal artifacts that result from dental fillings. In order to implement the operating plans created on the basis of the data on the computer, templates are used whose positioning must correspond in the reference system of the patient data and in the reference system of the patient himself. To achieve consistency, the templates are registered relative to the patient. For this, the coordinates of the "real world" of the patient are brought to coincide with the world of the corresponding data set and the planning based thereon.

The templates themselves are usually created on the basis of dental models, whereby the dental models also have to be registered in relation to the patient data. For this purpose, the following methods are known to be used:

On the one hand, it is known to carry out the registration by means of radioopaque markings, which are recognizable both visually and in the 3D X-ray data record. These markers must be inserted into a pre-scored bite track worn by the patient during the scan. The radiopaque markings create a reference system that has a defined geometric relationship to mechanical interfaces, to the patient or even to tools to be machined. In the reference system thus defined, the operation plans planned on the computer can be implemented. The problem of this technique is firstly that an individual bite bar must be made. In addition, special markers are needed.

It is also known to computationally perform the registration by adjusting the surfaces. For this purpose, the surfaces of the teeth are determined from the patient data on the one hand and from data sets of the dental model on the other hand. Then the surfaces are superimposed by means of a registration algorithm so that the two data sets correspond. The disadvantage is that this method is susceptible to interference, since a complete coincidence of the surfaces is not possible. This is especially true when the quality of the patient's admission is affected by metal artifacts. The recordings of the tooth model can thereby be generated optically, for example with a laser scanner, and registered with the corresponding data record of the patient, which is generated by means of x-ray imaging. So far, two devices are needed, which is associated with a high expenditure on equipment.

DE 197 25 197 A1 shows a system in which the patient is fixed during a recording via reference elements in the form of earplugs, wherein marker webs form a coordinate system. By means of a bite fork on which the patient bites, the plaster model of the jaw can be held in the corresponding position in the articulator with respect to the receiving plane (Camper's plane).

The object of the invention is now to provide a method and a system that can be inexpensively implemented with simple means and that allows for easy and practical handling precise registration between the recorded on a patient volume image data and a model of the corresponding body part of the patient. In addition, it is an object of the invention to provide a method for simple and reliable registration of control recordings

These objects are achieved by the method of claim 1, the system of claim 7 and the method of claim 12. Advantageous embodiments of the invention are mentioned in the respective subclaims.

The essential basic idea of the invention resides in a registration, which uses exclusively mechanical means, in particular a universal, for all necessary for the planning and production devices, such as the tomographic recording device and the drilling and milling device, normalized mechanical interface operated. This is possible because the reference system is only defined by a fixation device holding the patient and the model in the same position. This defines the immutable position of the patient and forms the reference system, without the need for an external reference system. For fixing the model in the same position, a holder is provided, which holds the model in the fixing device.

The model is after the recording of the patient data by means of the holder, which is in a defined position to the fixing device, first positioned in the appropriate position on the fixing device before it is fixed together with the holder. Holder and model thus form a unit that is in fixed relation to the fixing device. At this unit further steps required in the planning can be made.

It is not necessary that the positioning of the model on the holder is done on the fixing device held in the recording device. On the other hand, it is advantageous if the fixing device is first removed from the position on the recording device and attached to a stand which is independent of the recording device and which can be located in a laboratory. In this state, the model can then be positioned and fixed by means of the holder. Since the holder is in a defined position to the fixing device, also their position in relation to the recording device and thus to the patient data is known. Optionally, then fixed in the holder model for a scan on the recording device are positioned, the holder, as will be described below, ideally in a corresponding receptacle on the recording device is held in particular by means of an adapter.

A particular advantage of the invention is that with the proposed method, the registration between the dental model and patient data with one and the same recording device, in which the patient and the model are kept in the same position, can take place. Another device, such as a laser scanner, is not required. With the help of the invention, an exact representation of the teeth is also possible, which can be used as a basis for computer-aided planning systems. Thus, the occlusion, so the actual spatial positional relationships of the teeth to each other, can be included. The mechanical registration according to the invention can serve as a basis for the application of known CAD / CAM techniques to the tooth model, with which templates for intraoperative use are created. On the other hand, the tooth model registered according to the invention offers a detailed representation of the anatomy of the patient with his occlusion. The existence of the complementary data records results in a large number of possibilities for image processing. Further advantages of the invention are the reduced radiation exposure of the patient and the high accuracy of the registration. Since the tooth model can be recorded with the same device as the patient, there are advantages in logistics and a reduction in costs due to the reduction of the apparatus expenditure. The invention thus increases the incentive for the production of templates, which reduces the risk for the patients during surgery.

It is particularly advantageous if, during the registration as a fixing device, a bite-off with, in particular, a horseshoe-shaped biting surface is used. The bite may be part of the recording device, which advantageously has a mechanical interface for fixing, in which the bite may possibly be inserted by means of a corresponding adapter and thus releasably fixed. During registration, the removable bite bar is fixed in a defined position to the imaging device via the adapter. In the implementation of the method, the Aufbißfläche is now fed from above and / or from below with fast-curing impression material to which the patient bites and then hardens within a short time. Now the patient who is fixed on the bite in a defined position to the imaging recording device can be scanned.

According to the bite for creating a registered data set of the dental model, including the cured impression mass on the recording device is left fixed while the tooth model is inserted into the impression mass. Since the patient and tooth model are the same structures, the tooth model fits exactly into the impression mass and is thus in the position of the patient's teeth in the 3D volume data set. Then the fixing device removed and made a recording of the tooth model with the recording device. The advantage of taking the tooth model is that the image data of the tooth model are not affected by artifacts, as there are no metallic objects that cause such artifacts in the tooth model. Since no radiation protection is required for the tooth model, this can be recorded with high-dose radiation, thereby achieving optimum image quality. The dental model and the patient's teeth are in exactly the same position in relation to the recording device in both images and are thus registered. By means of image processing, for example, the two data sets can be fused together in such a way that the high-resolution artifact-free recording of the teeth occurs instead of the poorer recording of the actual teeth of the patient. In this case, the image data of the patient and the model can be arithmetically superimposed without transformation of the reference system.

For further computer-assisted or manual processing of the tooth model, other planning steps can also be undertaken on the model fixed on the holder. Thus, the model fixed on the holder can be removed and clamped in the receptacle of a processing device, in particular a drilling, sawing and / or milling device. In this case, the recording of the processing device on the specified geometric conditions in a defined relation to the fixing device.

In order to avoid a coordinate transformation, the fixing device and the holder can use the same mechanical interface. However, it is not much more expensive to provide different interfaces, which, as I said, in a defined geometric relationship to each other. The steps of the surgical procedure, in particular the introduction of a drilling channel and the adaptation of an implant, can then be simulated based on the image data of the patient on the tooth model registered in this way.

With the invention, high-quality representations of the oral and facial regions can be created. In particular, with the known Positioning the patient in the dataset and the artifact-free representation of the teeth and the mucous membrane a number of image processing advantages. The mechanical registration creates optimal conditions for even more accurate, image-based registration procedures, since an optimal starting point is now defined.

The invention will be explained in more detail with reference to Figures 1 and 2. Show it:

Figure 1 shows a device for registration with two interfaces and

Figure 2 shows a device for registration with an interface.

In Figure 1, a tripod 1 is shown as it may be placed in the laboratory of a dental technician. In the stand 1, a recording socket 2 designed as an interface is provided, into which a bite block 3 can be inserted as a fixing device by means of a plug-in element 4 attached thereto (arrow A). The bite 3 is loaded with mitlerweile hardened Aufbissmasse 5, in which a patient had bitten into it and left his dental impressions 6. These are also present on the bottom but not shown. While the patient had clamped the bite 3 between his teeth, a scan made patient data from him, the bite block 3 being inserted in a corresponding socket of the receiving device, in particular the Cone Beam device.

After preparation of the patient data representing the jaw in its three-dimensionality, the bite 3 is moved to the stand 1 and a tooth model 7 is inserted from below into the bite 3 by the patient. For the maintenance of the tooth model 7 provides in this case a support 8, to which the tooth model 7 by means of a high-build adhesive 9, such as plaster, is glued. The support 8 itself is placed on a base plate 11 (arrow B) and held by fixing pins 10 and corresponding holes 12. About the adhesive 9, the tooth model is held in an exact position in the bite 3, wherein the support. 8 and the base plate 11 are in a defined orientation to the stand 1. In this case, the base plate 11 is fixed to the tripod 1.

Such a base plate 11, in particular the same, can be mounted in the corresponding position on the recording device. After placement of the tooth model 7 by means of the support 8, a scan of the dental model 7 can be made, which is purely mechanically in the same position as before the patient.

In addition, the serving on the support 8 as support can be removed from the receiving device and also defined via the fixing pins 10 are clamped in a device for further processing. In this case, the fixed on the base plate 11 support 11 serves as a fastening means which allows a fixation of the model in the fixing device and ensures the maintenance of the model in this position after removal of the fixing device.

The base plate 11 thus has on its upper side with the holes 12 via a defined mechanical interface. The geometric relation of the mechanical interface at the top of the base plate and the stand 1 for the bite is defined and known. So the exact positioning of the support 8 is possible. Also conceivable is an embodiment of the transfer device, in which the holder for the bite is displaceably mounted in order to facilitate the Eingipsvorgang. Another embodiment is conceivable in which a support is additionally mounted above the bite, so that both upper and lower jaw can be transferred in one operation.

Also in Figure 2, such a tripod 1 is shown, which is in a defined position to the receiving device and has a trained as an interface receiving socket 2. In this case, there is a universal adapter 13 as a plug-in element, on which the bite 3 is releasably secured and over which it can be inserted into the receiving socket 2. During the recording of the patient data, the bite 3 was via a corresponding receptacle 2 on Recording device held. As in the previous embodiment, the bite 3 remains on the stand 1 until the tooth model 7 is inserted and fixed from below.

In this embodiment, however, the support 14 is fastened directly to the adapter 13 via a support arm 15. For this purpose, a connector 16 is provided. After attaching the support 14 on the adapter 13, the tooth model 7 is again fixed by means of a relining formed by a building adhesive 9 in the intended position on the bite 3. Now, a scan of the tooth model 7 is made, which is in the same position as before the patient due to the erfindunsgemäß purely mechanical means. The support 14 can also be removed from the receiving device and also clamped on the adapter 13 to a device for further processing. In this embodiment, a universal interface is realized with the adapter 13 and the receiving sockets 2, with which all needs can be solved to the registry in the field of preoperative planning.

According to the invention, in both exemplary embodiments, after the patient data has been recorded, the model is positioned by means of a holder in a corresponding position in the fixing device, wherein the holder is in a defined orientation relative to the fixing device. The model is then fixed on the support via the relining in this position so that further planning steps can be undertaken on the model fixed on the support.

The individual steps of the registration are summarized below:

1. Production of a dental model for the patient to be scanned by means of conventional technology.

2. Load a bite with fast-curing impression material, eg silicone. 3. Bite the patient on top of the loaded bite and allow the impression material to cure.

4. Scanning the bite-fixed patient e.g. with X-ray scanner.

5. Position and fix the tooth model to the bite

6. Scanning the tooth model with the same X-ray scanner.

7. Overlay the scans of the patient and the tooth model ("registration").

By registering the dental model with a patient's radiographic record, a number of applications are now possible, as shown below:

Production of a drilling template:

1. Remove the bite and tooth model from the recorder.

2. Transmission of the registration by means of the device described on two editions, on each of which the model for upper and lower jaws are fixed. The pads have a unique mechanical interface whose geometric relationship is known and defined for receiving the bite.

3. Positioning of the tooth model by means of the support on a drilling and / or milling device. This will transfer the registration.

4. Manual production of the drilling template according to known dental techniques based on the dental model.

5. Planning of the holes to be drilled, cuts, glands, osteotomies, or other surgical procedures in the registered patient and dental model dataset. 6. Transfer of the planning to the CNC machine or output of the planning data for the setting of manually operated drilling or milling devices.

7. Computer-controlled drilling or milling through a CNC machine into the drilling template or manual drilling / milling according to planning data.

Thus, drilling templates for implantology and the placement of distractors or miniplates can be created. In addition, by cutting a surface on the fixed to the teeth templates and cutting and / or sawing surfaces are created, which guide the respective instrument of the surgeon.

The above-described fixing device, which is designed in particular as a bite, is not only suitable in the context of the illustrated method, in which an operative procedure is planned on the basis of a body part of the patient and a model of the body part. Such fixing devices provided with hardened impression material and thus individually adapted to the patient can also be used in methods for generating and registering in chronological order a patient data taken in particular with a body part in its three-dimensionality and recorded by a recording device. For this purpose, the patient is held during the recording of the patient data with the corresponding body part in the fixing device, which is mounted in a defined position with respect to the recording device. The particular advantage is that the patient is firmly fixed in the receiving space of the recording device in a reproducible manner.

According to the invention, the fixing device is charged with an impression compound before the body part of the patient is pressed into the impression compound and the impression compound is cured. Then the first patient data is recorded. At a later time, a further recording of the patient positioned with the same body part in the hardened impression mass is made. The data sets of successive recordings produced in this way can, in particular by calculation, be used without further coordinate transformation compared with each other. It is particularly advantageous if a particular horseshoe-shaped bite is used as a fixing, which is fed with impression material.

The fixation device, in particular the bite, can thus serve for patient fixation and for registration of images of the patient that were taken at different points in time. This registration of a temporal sequence of images is made possible by the highly reproducible positioning of the patient held by the bite in the recording device. This simple procedure is particularly useful for the follow-up of diseases and the success of therapies.

As shown, the consistency of the mechanical interface on the device as well as the reproducible positioning of the patient on the fixation is the most important prerequisite in this procedure. According to the invention, the body part, in particular the jaw (upper or lower jaw) is selected as an anatomical structure of relatively constant shape and with suitable geometric and biomechanical properties for taking impressions. On the other hand, an impression material is used which is dimensionally stable over longer periods of time and has suitable elasticity in the case of undercuts. Since a virtually unlimited number of recordings distributed over long periods of time is possible with such a fixing device charged with impression material, the fixing device should be disinfectable.

The procedure according to the invention for the preparation of an initial recording can proceed in the following steps:

1. Feeding a fixing device, in particular in the form of a horseshoe-shaped bite, with curing impression material.

2. Taking an impression on the patient.

3. attaching the fixing device on the imaging device by means of a defined interface. 4. Position the patient in his previously created impression.

5. Perform a scan.

6. Release the patient from the impression material.

7. Remove the fixing device.

Control recording can be done in the following steps:

1. attaching the already provided with an individual patient's impression fixation device on the imaging device by means of a defined interface.

2. Position the patient in his previously created impression.

3. Perform a scan.

4. Release the patient from the impression material.

5. Remove the fixing device.

Claims

claims

A method for planning a surgical procedure on a body part, in particular on the jaw, of a patient, wherein as part of a registration a common reference system is defined between a set of patient data taken with a recording device and representing the body part in its three-dimensionality, and a model of the body part, wherein the patient is held during the recording of the patient data with the body part in a fixing device (3) which is mounted in a defined position with respect to the recording device, characterized in that the model (7) after receiving the patient data by means of a

Holder (8) is positioned in a corresponding position in the fixing device (3), wherein the holder (8) in a defined position to

Fixing device (3) is that the model (7) is fixed in this defined position on the holder (8) and that further planning steps on the on the holder

(8) fixed model (7).

2. The method according to claim 1, characterized in that the fixing device (3) is removed from the position on the recording device and on a stand independent of the recording device tripod (1) is held before the model (7) by means of the holder (8) and fixed becomes.

3. The method according to claim 1 or 2, characterized in that in a further planning step, the fixing device (3) is removed and a recording of the model (7) is made with the recording device, wherein the model (7) in the same defined position as before the patient is located, wherein the image data of the patient and the model (7) are mathematically superimposed without transformation of the reference system.

4. The method according to claim 1 or 2, characterized in that in a further planning step, the on the holder (8) fixed model (7) together with the holder (8) and removed in the recording of a processing device, in particular a drilling and / or milling device is clamped, wherein the receptacle is in a defined relation to the fixing device (3).

5. The method according to claim 4, characterized in that steps of the surgical procedure, in particular the introduction of a drilling channel and the adaptation of an implant, are simulated on the model on the basis of the image data of the patient.

6. The method according to any one of the preceding claims, characterized in that a bite (3) with impression material (5) is used as fixing, which is hardened in the bite of the patient.

7. A system for defining a common reference system ("registration") comprising a tomographic recording device for receiving a set of patient data, comprising a fixing device (3) for the defined positioning of the patient during the recording and comprising a model (7) of the body part to be recorded by the patient , in particular of the jaw, characterized in that the fixing device (3) has a mechanical interface (4), by means of which it can be detachably fastened to the receiving device in a defined position, and in that a fastening means (8, 11) is present, which has a fixation allows the model (7) in the fixing device (3) and that ensure the maintenance of the model (7) in this position after removal of the fixing device (3).

8. System according to claim 7, characterized in that the fastening means (8,11) has a mechanical interface (4,13) with which it is held in a defined position on the recording device.

9. System according to claim 8, characterized in that the fastening means (8, 11) can be held in a defined position via the mechanical interface on a machining device, in particular a CNC machine / drilling / milling unit.

10. System according to any one of claims 7 to 9, characterized in that the fixing device is a bite (3).

11. System according to claim 10, characterized in that the bite and / or the fastening means via an adapter (13) is detachably secured to the on the recording device or the processing device in a defined position.

12. A method for generating and registering in chronological order with a recording device recorded in particular three-dimensional patient data of a body part, in particular of the jaw, a patient, wherein the patient is held during the recording of the patient data with the body part in a fixing device (3) defined in Position is mounted in relation to the recording device, characterized in that the fixing device (3) with an impression compound (5) is fed, that the body part of the patient is pressed into the impression compound and the impression material (5) is cured and that the first patient data are recorded that at a later date, another shot of the with the

Body part in the hardened impression mass (5) positioned patient is made that the records of successive recordings are compared.

13. The method according to claim 12, characterized in that a particular horseshoe-shaped bite (3) is used as a fixing, which is fed with impression compound (5).