DE102012002817B4 - Method for determining digital data sets for the production of dental prostheses - Google Patents

Abstract

Process for the production of dental prostheses, a prosthesis, a model or a framework construction, characterized in that the following process steps follow one another: a. The patient is being prepared. A gingiva preparation with the aid of thread technique or electrotome is not performed. b. To determine the jaw relation, the patient is in the final bite. The patient bites either on a provisional made in the appropriate bite or on a thermoforming splint. c. The X-ray machine used for recording is set up for digital volume tomography (DVT) and is Hounsfield-calibrated. d. Data is generated with a scan. From the acquired raw data, a 3-D DICOM data set is reconstructed. e. First Segmentation: From the 3-D DICOM dataset, the voxels are separated, which according to their Hounsfield density values are in the segments for bone, enamel, dentin and root cementum. The voxels that are in this segment of the Hounsfield scale are stored in the first 3-D object. f. Second segmentation: The 3-D dicom data is segmented again. Voxels are included in the segment of Hounsfield density values for implants and abutments. The storage takes place in the second 3-D object. G. Both 3-D objects are finely adjusted by visual inspection. H. Both 3-D objects are chiseled. i. Both 3-D objects are spent in the format STL. j. In STL format, unique 3-D surface objects are generated, superfluous information is deleted. k. From the two individual objects, a final primary data record in STL format is generated. l. Using this primary data set in STL format, the "rapid manufacturing" process transforms the virtual computer-generated model into a real model using the following methods: milling, 3-D printers, laser sintering, stereolithography.

Description

The invention relates to using a Hounsfield calibrated digital volume tomograph to generate a medical 3D dataset on an anatomical structure in the oral and maxillofacial region and then selecting the desired data using Hounsfield density values to make a prosthesis, a model or a prosthesis scaffold construction. The invention further relates to a method for generating a medical 3D data set with which, after data segmentation and conversion into a suitable data format, directly dentures, models or scaffolding constructions can be produced.

The use of digital computer tomographs (DVT devices) in dentistry for generating medical 3D data sets is known (see, for example, US Pat. DE 10 2008 009 643 A1 or DE 10 2004 035 475 A1 ).

In the German version of the online encyclopedia "Wikipedia" the digital volume tomography (DVT) is described as follows on the filing date of the present application: The digital volume tomography is a three-dimensional, dental and ear, nose and throat imaging tomography method using X-rays , In English-speaking countries, the term "Cone-Beam CT (CBCT)" is customary for this process. Similar to computed tomography or magnetic resonance imaging, DVT (in digital dentistry, previously digital, now dental volume tomography) enables the generation of sectional images. In the DVT, an X-ray tube and an opposing image sensor revolve around a lying, sitting or standing patient. The rotating about 180-360 degrees X-ray tube emits a conical, mostly pulsed X-ray (X-ray flash). The X-ray radiation penetrates the three-dimensional examination area and generates on an flat panel detector with a scintillator layer an attenuated gray-scale X-ray image as a 2D parallel projection. In the process, objects outside the focal plane are blurred due to movement. During the rotation of the X-ray tube, a large series of two-dimensional or line-shaped individual images is recorded, whereby the circular-rotating image series directly produces a fluently observable 2D panorama image. With a subsequent mathematical calculation by means of a PC, an optimized panoramic image can be generated. Furthermore, a greyscale coordinate image in the three spatial planes can also be generated using correspondingly complicated methods. This three-dimensional coordinate model corresponds to a volume graphic composed of individual voxels. From this volume, sectional images (tomograms) can be generated in all spatial levels as well as 3D views of body regions. The imaging time of up to 30 seconds can sometimes result in camera shake ("artifacts") that can negatively impact the quality of the imaging because they can not be completely mathematically eliminated during algorithmic processing. Metallic objects such as dental plugs can also create unwanted image noise, as they cause the beam z. T. completely absorb and shade behind it.

At least two treatments are usually needed to make dentures. In the first treatment, the teeth to be restored and their surrounding gums are prepared. For this purpose, the relevant residual teeth are ground down to a stump. It forms a step in the hard tooth substance, the so-called preparation border. If this preparation margin is below the gum, the gum is also prepared. To do this, thread circularly between gum and tooth. As a result, the gums are splayed from the tooth to give the impression materials used later, the possibility to reach the preparation margin.

Especially with extensive dentures this first preparation for the dentist is very complex and painful for the patient. The preparation of the preparation border is particularly important, since there the transition to the dentures will lie.

In the first treatment, the upper and lower jaw of a patient is then molded by means of plastic curing impression or impression materials in order to obtain a so-called impression. The impression serves as a basis for the production of a model. On the model a dental technician forms the dentures, which is usually executed as a wax model. The wax model usually serves as a positive mold for a negative mold. The denture is obtained from the negative mold in a known artisanal way. In the second treatment, the dentures are now adapted and used in the patient.

Based on the present state of the art, the object now was how to make the manufacture of dentures less painful and stressful for the patient, which is also inexpensive and easy.

The publication WO 2011/077 175 A1 discloses a method for making removable prostheses in the 3-D printing process. According to the prior art, these prostheses in the Created in a wax model, which was molded the patient's jaws, teeth are pressed, which are industrially prefabricated from wax. This model is then "countered": it is covered with plaster, which is heated after curing so far that the wax melts out. In the resulting mold, the prosthesis is cast from suitable plastic.

In contrast, in WO 2011/077 175 A1 suggested that the prosthesis is made directly with a 3-D printer, but it is not disclosed how to obtain the data that the 3-D plotter can handle.

In the publication WO 2012/016 635 A2 a method is disclosed for radiographing a patient in the final bite. According to the state of the art, the object here was to avoid image effects that occur in the occlusion area. The task is solved with a bis insert. The process objective is dental treatments such as the treatment of Dysgnathin.

In the thesis of Marion, Jähne: Automatic extraction of the heart from contrast-enhanced tomographies of the Torax, Darmstadt University of Technology, Department of Mathematics, carried out at the Fraunhofer Institute for Computer Graphics, November 2005, page 4, the Hounsfield scale for the standardized comparison of CT Pictures described.

The inventors have now found a method that drastically simplifies the fabrication of dental prostheses by using a 3D medical dataset after data segmentation (object masking) and conversion to a suitable data format for the direct fabrication of dentures, a model, or a scaffolding design 3D data set is determined directly on the patient and the production via a process of rapid production, the so-called "rapid manufacturing" takes place.

In this way, the step of impression taking and thus also a part of the first treatment, namely the patient's most painful presentation of a preparation border, can be omitted.

The invention thus relates to a method for generating a medical 3D dataset, a so-called 3D-DICOM dataset, with which, after data segmentation (object masking) and conversion into a suitable data format, dentures, master models or framework constructions can be produced directly and the following steps (i) to (iv) comprises:
Step (i): generating a 3D DICOM record of a previously prepared denture and gum, wherein the gum may contain prepared tooth stumps, implants and possibly abutments, using a Hounsfield calibrated digital volume tomography and storing the 3D DICOM record on a data carrier;
Step (ii): segmentation (object masking) of data representative of tissue structures and the like (e.g., air, adipose tissue, water, bone, cementum, dentin, enamel, and other dentate materials) from their Hounsfield Density values and storing this segmented data as the first 3D object and then further segmenting the data on Hounsfield density values used for metal implants and abutments, e.g. Titanium and storing this segmented data as a second 3D object;
Step (iii): converting the first and second 3D objects obtained in step (ii) into a format, preferably STL format, suitable for use in a rapid manufacturing process; and
Step (iv): making a denture, model, or scaffolding design.

In an alternative embodiment [X], the invention relates to the method described above, in which, after step (iii), in a step (iii-a), by means of suitable data manipulation, a virtual model plus virtual prosthesis is created, optionally in another Step (iii-b) subtracts the original data obtained from manipulation to obtain a dataset describing the denture.

The data manipulation in the alternative embodiment [X] may be made based on existing data of anatomical structures (eg, scans of the patient's bit from damage or similar human teeth being scanned) that may have been processed.

In a further alternative embodiment [Y], in step (iii) the mucosal information of implants ("emergence profiles") is detected by picking up the information present in the dentition of the composite cuffs surrounding the abutments.

It goes without saying that a 3D data record is only made on the patient when there is a medical necessity, which is clearly ensured by a justified medical indication.

The invention further relates in one embodiment [A] to the use of a Hounsfield-calibrated digital volume tomography to generate a 3D DICOM. Data set on an anatomical structure in the oral and maxillofacial area and then selecting the desired data by data segmentation / object masking and converting this segmented / masked data into a format so that this data can be used in a rapid manufacturing process.

In another embodiment [B], the invention also relates to using a Hounsfield-calibrated digital volume tomograph to generate a medical 3D dataset on an anatomical structure in the oral and maxillofacial region, and then selecting the desired data using Hounsfield density values Production of a prosthesis, a model or a framework construction.

In a further embodiment [C], the invention relates to the use described in embodiment [B], wherein the anatomical structure is a denture and the method produces a dental prosthesis, a model or a framework construction.

The invention further relates in one embodiment [D] to the embodiment [C], in which for air a Hounsfield density value of -1000, for fatty tissue of -100, for water of 0, for bone 500 to 1500 and for implants and Enamel of 3000 is assumed.

• – Acteon Whitefox – Patientenpositionierung sitzend, stehend: Volumen Zylinder, 599 Images, FOV 60 mm × 60 mm, 80 mm × 80 mm, Auflösung 0.15 μm 105 kV, 9 mA, gepulst, Dental Scan 360°, 25 sek, effektiv 6,8 sek., Brennfleck 0.5, Hersteller: Satelec (Acteon Group) – de Götzen – Milano.
• – NewTom 5G – Patientenpositionierung liegend: Volumen Zylinder, 659 Images, FOV 60 mm × 60 mm, 80 mm × 80 mm, Auflösung 0.125 μm 110 kV, 16 mA, gepulst, Dental Scan 360°, 36 sek, effektiv 7,3 sek., Brennfleck 0.3, Hersteller: QR srl – Verona IT.

The digital volume tomographs (DVT devices) usable in step (i) are commercially available. Known and inventively preferred Hounsfield-calibrated DVT devices are, for example:

• - Acteon Whitefox - Patient Positioning Seated, Standing: Volume Cylinder, 599 Images, FOV 60mm × 60mm, 80mm × 80mm, Resolution 0.15μm 105kV, 9mA, Pulsed, Dental Scan 360 °, 25sec, Effective 6, 8 sec., Focal spot 0.5, maker: Satelec (Acteon Group) - de Götzen - Milano.
• - NewTom 5G - patient positioning lying: volume cylinder, 659 images, FOV 60 mm × 60 mm, 80 mm × 80 mm, resolution 0.125 μm 110 kV, 16 mA, pulsed, dental scan 360 °, 36 sec, effective 7.3 sec ., Focal spot 0.3, manufacturer: QR srl - Verona IT.

These devices are usually connected to a computer running the appropriate software (controller) to operate the device. The Acteon Whitefox is the ActeonWhitefoxControl.ce.0434 and the NewTom 5G is the NewTom NNT ^TM . According to the invention, data carrier means all usable data carriers (eg hard disks, chips, CD-ROMs, DVDs, Blue-Ray disks).

The segmentation (object masking) of data representative of tissue structures and the like as described in step (ii) (eg, air, adipose tissue, water, bone, cementum, dentin, enamel, and other dentate materials) of their Hounsfield sealing ranges, calibration of the DVT device according to the Hounsfield scale is absolutely necessary. Each voxel can be uniquely assigned values between -1000 and +3000 Hounsfield. Air, for example, has a value of -1000, fatty tissue of -100, water of 0, bone 500 to 1500; Implants and enamel of 3000.

In medical computed tomography, radiopacity (radiodensity, x-ray attenuation) values are converted into CT numbers according to the standard Hounsfield Unit (HU) scale. This procedure is also used on Hounsfield calibrated Cone Beam CT (DVT) devices.

The formula for this is:

Segmentation (object masking) in accordance with the invention means filtering the data according to Hounsfield density values. Air -1000; Fatty tissue -100; Water 0; Bone 500 to 1500; Implants and Enamel 3000. As previously mentioned, the prerequisite for segmentation (object masking) of the 3D-DICOM dataset is air, water, adipose tissue, bone, cementum, dentine, enamel, metals, and other materials in the oral and maxillofacial region , is the calibration of the DVT to Hounsfield. The Hounsfield calibration is to be performed regularly, preferably weekly. The procedure for the calibration is described in the documentation for the quality assurance of the respective manufacturer z. As Acteon or New Tom clearly described.

For the segmentation (object masking) of the 3D-DICOM data set according to the invention in step (ii), the OnDemand3D ^™ App 3D software (version 1.0) can be used. OnDemand3D ^TM App allows the management of medical 2D and 3D images. Extensive 2D and 3D tools for analysis, formatting and segmentation of data are provided.

The data in step (i) are generated as follows: After scanning according to the invention in volume size 80 mm × 80 mm high-quality according to step (i), the 3D-DICOM data record is reconstructed from the acquired raw data. The resolution is 1.25 μm or 1.5 μm. The captured 3D DICOM record is taken from the Acteon Whitefox Imaging ^TM or NewTom NNT ^TM software was exported as a 3D DICOM record. Subsequently, in step (ii) the 3D-DICOM data record is read into the software OnDemand3D ^TM App. The object mask tool segments (masks) such data from the DICOM records that represent bone, enamel, dentin, and root cementum. The mask used is "Used Threshold" Limits: 1000 HU-6000 HU. This segmented data is stored in a first 3D object.

As a result, the shape of the tooth preparation can be detected in three dimensions. The surfaces of prepared teeth can thus be displayed. In the second step, the 3D-DICOM data are segmented by implants. The mask used is "Used Threshold" Limits: 2700 HU-6000 H. These are stored in a second 3D object. For fine adjustment, a visual inspection of the masked objects is carried out. If necessary, the masking windows are minimally adjusted.

The 3D objects 1 and 2 are separated from unnecessary parts by the "chisel" function in the object mask tool, which means that superfluous regions are removed.

In step (iii), the objects 1 and 2 thus generated are stored as individual STL files via the surface generation option of the OnDemand3D ^™ App software "Save to STL". For the export, the compression is set to 0.100 and the filter function is deactivated.

The individual STL files are then read into the software 3D-Tool Version 10 Basic. The 3D-Tool software is used for professional data processing for the later rapid manufacturing, in particular rapid prototyping. 3D Basic Import, 3D Base Formats: STL, VRML, SLP, XGL, OBJ, PLY, 3DS, ASC, DXF, IV. Simultaneously load multiple files to 3D models or 2D drawings. Import / export STL files, import and export models in STL format.

Unique 3D surface objects are created in the 3D-Tool software: OK (bone, root cementum, dentin, enamel) OK implants, UK (bone, cementum, dentin, enamel) UK implants; further unnecessary information is deleted. Subsequently, a final primary data record is generated from the individual imported STL objects. This is exported as a primary data record in STL format and is used for further processing in rapid prototyping.

The rapid manufacturing processes, also called rapid prototyping, which can be used in step (iii), are processes that start directly from the virtual, computer-generated model and produce the corresponding real model. Examples of such methods are milling processes (eg Contur-Crafting (CC) milling processes) or additive or additive manufacturing processes (3D printers, laser-sintering, stereolytic processes).

If a milling method is used, the data is transmitted in the appropriate format, preferably STL format, to, for example, a CC mill, which then mills out the desired scaffolding or model from a block (step (iv)). STL data is the data commonly used in rapid manufacturing to produce information stored in the data (i.e., shaped bodies).

The method in the manner claimed and described here is new and has hitherto not been possible due to the technical limitations on the part of the DVT devices. Since Hounsfield-calibrated DVT devices are available whose resolution is very good, the individual gray levels can also include air, water, adipose tissue, bone, cementum, dentin, enamel, metals, and other materials in the oral and maxillofacial area, according to their needs Hounsfield density, to be assigned. Only by this assignment, it is possible, after receiving the teeth or other anatomical structures in the oral and maxillofacial area, to deliver 3D DICOM data in the required quality. Of course, it is conceivable to use this principle to produce not only dentures, but also prostheses in other parts of the body, in particular oral and maxillofacial area in whole or in part.

Step (i) is performed exclusively on the living being (human or animal). Data recording on artificial dentures or on reproductions of artificial dentures is possible in principle.

The term "dentures" in the context of this invention has the same definition as in dentistry. As already mentioned, it is conceivable not only to produce dentures with the method according to the invention, but also to replace other structures of the human body.

The term "abutment" is generally understood to mean attachment and assembly elements used in implantology and aesthetic dentistry. Abutments serve as the basis for a crown and are often attachments on an implant.

The method according to the invention will be described with reference to the following embodiment without, however, restricting it to these.

Example 1:

Preparation of the patient: On the first day of treatment, the teeth or dental implants to be supplied with the abutments are prepared so that they are later suitable for receiving dentures. No aids (threads, electrotome) are needed to visualize the preparation margin. Subsequently, the production of suitable temporaries made of known composite material (Protemp 4 ^TM from 3M ESPE) using a thermoforming rail.

Step (i): On the same or next day of treatment, the patient is scanned using a Hounsfield-calibrated DVT device. When recording, the patient, supported by the temporary or the Tiefziehschiene, in the final bite, so that the jaw relation is unique. Scanning creates the desired 3D DICOM record. The patient should not move during the scan. As mentioned above, both the thermoforming splint and the temporaries can be used for jaw relation determination. This is necessary to represent the arrangement of upper to lower jaw in the final bite. If the jaw relation determination is wrong, a wrong final bite will be created.

a) Jaw relation determination with the aid of a temporary restoration:

This variant is interesting if the bite was disintegrated by the preparation of the teeth. Ie. there are only bite contacts from tooth to temporary and not from tooth to tooth. This radiopacity of the temporaries should differ significantly from the other radiographic opacities in the mouth. Thus, the temporaries in the generated 3D DICOM data set are then well segmented in step (ii). The patient is allowed to bite on the provisional prepared in the appropriate bite during the recording. Later, segmentation of the data reveals upper and lower jaw without temporaries. Thus, the dentition can be seen in the correct jaw relation without touching upper and lower jaw teeth.

b) Jaw relation determination with the aid of a thermoforming rail:

This variant is possible with all dentures. The patient wears the thermoforming splint during the recording. The Tiefziehschiene can sit on the upper or lower jaw teeth. It has a layer thickness of about 0.5 mm and a barely detectable radiopacity. Consequently, the record shows a slightly raised bite. The individual teeth disklude and can therefore also be represented as individual objects. When creating the dentures can be decided whether in the articulator (simulator for chewing movements) the bite z. B. lowered again, so that teeth on which no dentures is created, again in contact.

Step (ii) and (iii): The data thus obtained are segmented / masked as described above and converted into an STL data format as described above.

The further procedure for the creation of the denture with the help of the described data set offers two variants:

Variant a - step (iii-a)

The segmented and STL-formatted data set (primary STL data set) is supplemented by block-shaped blocks, so that a one-piece virtual model is created.

At this point, it is possible to make a model using rapid manufacturing techniques (eg milling machine, 3D printing or stereolytic process) based on STL data. The resulting models are similar in shape to the well-known in dentistry preparation models with the difference that upper and lower jaw model are interconnected. Both models are transferred to an articulator. The use of a facebow is recommended. The model is then separated into an upper half of the jaw and a lower half of the jaw. With the help of these models, the dentures are now created in the usual way.

Variant b (step iii-a)

It is also possible to continue to operate the production process virtually. Ie. one maintains the STL data record in a special software, z. B. Girrbach ceramill mind. In this software you have comparable to the real articulator a virtual articulator. In addition, it is possible to expand the illustrated preparation stumps and abutments to the final tooth shape (virtual growth). It would then be possible to make this process (virtual growth) free, and it would also be possible to resort to a database that offers ready-made tooth forms (eg tooth 11 the mirrored form of tooth 21, at 35 the mirrored form of 45 etc.) ,

It is also interesting to use records of relatives but also strangers for virtual growing up. This process creates an extended dataset showing the finished dentition.

From this, the primary STL data set is subtracted so that the data set of the denture remains (step (iii-b)). This final data record is sent to a milling machine, z. B. Girrbach, transferred to manufacture the dentures.

Example 2:

A 37-year-old male patient is due to the medical indication 10 immediate implantation and prosthetic restoration by means of bite increase, backward planning and single-tooth concept received.

Treatment: After completed periodontal and conservative pretreatment with closed curettage and composite abutments, 10 immediate implants (regio 12-22, regio 24-26, regio 44-46) were inserted with a time delay ( - ). Subsequently, the preparation of the teeth requiring treatment 36-37, 14-15 and 13, 23 for partial ceramics. A gingiva preparation with the help of thread technique, electrotome, etc. was not performed. The patent was subsequently supplied with plastic temporary restorations made using thermoforming slides. The deep-drawing rails were created on duplicates of models after wax-up, on which the results of the patient's final bite increase were incorporated.

After the implantation and the preparation was not molded, no bite registrations were made in the mouth. Instead, the information listed below was obtained from an existing DVT scan, which was then converted from 3D DICOM format to STL format. For precise orientation of the implants and surgical control, digital volume tomography was performed pre- and postoperatively. In each case a FOV (Field of View) of 80 mm × 80 mm, 360 ° rotation, 110 kV tube voltage and automatically adjustment of the current (mA), the so-called "Safe Beam Technique" was selected. To reduce the dose, an effective irradiation time of up to max. 5 seconds dialed. The low irradiation time is achieved by pulsed high-frequency tubes. For sharpening the devices a focal spot of 0.3-0.5mm is necessary. Essential for the good segmentation of the 3D DICOM data is the calibration of the Hounsfield device. Suitable devices are: Acteon Whitefox and NewTom 5G.

The conversion of the 3D-DICOM data into STL format was carried out via the 3D reconstruction software with STL interface (SurfaceTesselationLanguage, description of the surface by triangles or standard triangulation LANGUAGE). The STL records were created by the 3D reconstruction software. For this purpose, individual objects were prepared for the preparation impression and implant impression. From these objects, STL Export was generated via the export function (Saue to STL) and surface generation option with high quality without filter.

Preparation impression: The DVT shows a variety of gray values. Special DVT devices are calibrated according to Hounsfield, so that the separation of the gray values is possible. In order to precisely grasp the shape of the tooth preparations three-dimensionally, the greyscale levels of enamel, dentin and cementum are extracted and used to create a data set that makes it possible to reproduce the surfaces of prepared teeth ( . . . ).

Implant Impression: Using Hounsfield segmentation, it is also possible to create a dataset that represents only titanium elements ( ). In most cases we recommend intraoperatively to screw in a special abutment designed for this procedure. Consequently, we see abutments and fixtures in the Titanium dataset. The two datasets described above are superimposed and virtually complemented in the basal portion by base boxes, so that a piece is created, which shows the elements in their correct three-dimensional orientation to each other.

Bissnahme: The DVT scan takes place in final bite position. In patients with a final bite unequal to the desired future bite relation (as in our case), this situation is simulated via a deep-drawing rail obtained by Backward Planning. This splint carries the patent during the scan and thus prevents records of unworked upper and lower jaw elements from merging.

The edited data set described above served as the basis for a rapid prototyping process. Here are from 3D data z. B. plastic models generated. In our case, a printed OK / UK plastic model was created. Since the model was made in one piece, then the separation into two halves took place. Previously, however, a bite key was created on the model, which continues to allow the three-dimensional alignment of the models to each other. The models were sawn and articulated. Thus, work documents were available, as the dental technician knows from classical prosthetic work.

In the laboratory, the model was scanned again and thus prepared for CAD / CAM technique. With the help of special software, the dentures were designed and placed in a virtual articulator. In the case of the abutments, the original dimensions were similar to a technical drawing as a record available. Therefore, all virtual abutments were swapped again for this record. Thus, an optimal fit of the implant crowns is guaranteed.

Subsequently, these elements were milled by means of CAD / CAM technology from hard wax and tried in the mouth. These hard wax crowns were then transferred in the case of teeth in ceramics and partially veneered. The implant crowns were again milled from plastic in the sense of a long-term temporary restoration.

Reason: Our model shows both tooth hard tissue as well as abutments in their three-dimensional orientation to each other. We do not see the gums. Thus, the emergence profile of the implant crowns was designed freely. The long-term temporaries therefore serve to prepare the gums for the maximum possible esthetic result. In the further course of treatment, the temporal temporaries are replaced by individual implant ceramic crowns. All 15 elements were integrated in one session.

and show the three-dimensional representation of the implants segmented by Hounsfield with ( ) and without upper and lower jaw ( ) of the patient.

shows the record as STL export for preparation presentation.

shows the implant data set as STL export, especially here the spatial orientation of the titanium elements 46-44 to each other.

shows a model that emerged from the DVT data using rapid prototyping.

shows an image in the upper jaw, the virtual abutments have already been exchanged for their original data records.

shows the upper jaw before insertion.

shows the method of the invention created dentures in the upper jaw.

Claims (1)

Process for the production of dental prostheses, a prosthesis, a model or a framework construction, characterized in that the following process steps follow one another: a. The patient is being prepared. A gingiva preparation with the aid of thread technique or electrotome is not performed. b. To determine the jaw relation, the patient is in the final bite. The patient bites either on a provisional made in the appropriate bite or on a thermoforming splint. c. The X-ray machine used for recording is set up for digital volume tomography (DVT) and is Hounsfield-calibrated. d. Data is generated with a scan. From the acquired raw data, a 3-D DICOM data set is reconstructed. e. First Segmentation: From the 3-D DICOM dataset, the voxels are separated, which according to their Hounsfield density values are in the segments for bone, enamel, dentin and root cementum. The voxels that are in this segment of the Hounsfield scale are stored in the first 3-D object. f. Second segmentation: The 3-D dicom data is segmented again. Voxels are included in the segment of Hounsfield density values for implants and abutments. The storage takes place in the second 3-D object. G. Both 3-D objects are finely adjusted by visual inspection. H. Both 3-D objects are chiseled. i. Both 3-D objects are spent in the format STL. j. In STL format, unique 3-D surface objects are generated, superfluous information is deleted. k. From the two individual objects, a final primary data record in STL format is generated. l. Using this primary data set in STL format, the "rapid manufacturing" process transforms the virtual computer-generated model into a real model using the following methods: milling, 3-D printers, laser sintering, stereolithography.

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