A system and a method for tooth root canal shape modeling

Abstract

The present invention relates to a system for tooth root canal shape modeling comprising an imaging device and a calibration stand, wherein the calibration stand comprises a body (1) comprising two arms (7, 8), with at least one reference element (2) being arranged on the upper surface of the body (1), and a measurement insert (3) comprising a canal part (4) and a base (5) part, wherein the body (1) is detachably connected with the base part (5) so that the canal part (4) extends perpendicular to the upper surface of the body (1) and substantially parallel to the reference element (2). The present invention also relates to a method for tooth root canal shape modeling.

Description

[0001] A system and a method for tooth root canal shape modeling

[0002] The present invention relates to a system and a method for tooth root canal shape modeling. The objects of the invention are applied in stomatology, in particular in prosthodontic treatment.

[0003] A significant challenge in prosthodontic treatment is to rebuild the pulpless tooth, which has a substantial coronal tissue loss. A non-limiting example of such a situation are damaged or broken teeth protruding by no more than 2 mm above the gum level. As preparation is impossible, the most common state-of-the-art prosthetic fillings used to reinforce the tooth root and allow the restoration of the lost tooth crown are standard post-and-cores typically made of glass fiber. Their clear advantage lies in the fact that their modulus of elasticity, being approx. 20 GPa, is similar to that of the dentine, which is approx. 18 GPa. Unfortunately, such fibers do not perfectly assume the shape of the tooth canal. Moreover, they have a circular shape, which increases the susceptibility of the structure to torsional forces and may lead to the decementation of the post-and-core. They also cannot bear axial loads on the root, which may cause the root to undergo a longitudinal fracture.

[0004] The above problem can be solved with the use of individual post-and-cores prepared in the laboratory and having an oval shape perfectly matching the shape of the tooth canal. In state-of-the-art, post-and-cores dedicated for individual patients are prepared with materials which can be worked (e.g. machined) for providing them with the final desired shape. Typical solutions thus comprise metal post-and-cores, including those made of titanium or gold, as well as ceramic post-and-cores having a significantly higher Young's modulus, above 150 GPa. The use of post-and-cores having Young's modulus significantly different than that of the dentine may cause the root to break or the post-and-core to decement.

[0005] In recent years, TRINIA, which is a glass-fiber-reinforced resin, has become a promising material used in the manufacturing of post-and-cores. This material is available in the form of discs suitable for processing in the CAD-CAM technology. Importantly, TRINIA has the Young's modulus of 18.8 GPa, which renders it a promising candidate in the preparation of individual post-and-cores. In all prosthodontic works performed in the CAD-CAM technology, also in the works related to the preparation of the post-and-core, it is important to very precisely match the shape of the restored structures, in this case of the shape of the tooth root canal, and to digitize this shape for the purpose of further works related to the processing of the material.

[0006] Document EP2626036B1 discloses a method for virtually designing a post-and-core restoration adapted for attachment in a damaged tooth of a patient, wherein the damaged tooth comprises a bore for receiving the post-and-core. The method for virtually designing the tooth restoration uses a scanning system which comprises a longitudinal root part and the base part. The root part is in the shape of a thin and long pin, which is introduced during the scanning procedure into the already drilled bore hole. The above document indicates difficulties when scanning narrow longitudinal elements, and thus in the method for virtually designing a tooth restoration, the root part in the digital image is replaced with a computer 3D model. When performing the method for virtually designing a tooth restoration, the post-and-core is scanned after being arranged in the hole drilled in the prepared tooth or optionally it is scanned together with the impression of the remaining teeth, when it is removed together with the impression. In the above solution, the shape of the post-and-core corresponds to the shape of the drill used in the preparation of the hole, and therefore it does not allow for optional oval preparation, natural recesses (naturally shaped canals having e.g. drop-shaped cross-sections), lack of preparation or a possible accidental excessive preparation.

[0007] Document EP2400919B1 discloses a system and a computer-implemented method of designing and / or manufacturing a post-and-core to match a bore of a tooth. The method comprises the obtaining of digital scans of the tooth structures, wherein the problem of the invention is to obtain a precise scan of a bore in a tooth, which is impossible to obtain with the use of traditional optical scanning methods. For this purpose, the geometry of the bore is scanned with the use of its impression, obtained together with the impression of the adjacent teeth. First, a bore is drilled in the prepared tooth, wherein the bore is performed with the use of a dental drill. The bore is scanned by scanning the impression material from the entire impression model. Importantly, the obtaining of an impression following such a method results in bacterial contamination from the saliva and makes it impossible to obtain an impression in the cofferdam. Moreover, the lack of scaffolding (the post introduced into the canal) during the obtaining of the impression results in the possible shift of the axis of the long part of the impression and in the possible change of shape, even due to a limited contact).

[0008] On the other hand, document CN111067650A discloses a digital pile-core impression acquisition and model building technology without gypsum, belonging to the technical field of pile-core restoration. In one of the steps, an impression of the restored tooth canal is obtained and after the impression compound has set, the impression is optically scanned on the outside with the use of the 3Shape D2000 device. The digital model is subsequently used to build a post-and-core with the use of the CAD / CAM or 3D printing technology. Importantly, the obtaining of the impression entails the risk of bacterial contamination among others from saliva. Additionally, the lack of the canal part when obtaining the impression increases the risk that the geometry of the impression is changed, and thus reduces the manufacturing accuracy of the final post-and-core.

[0009] The technical problem of the present invention is to provide such a system for tooth root canal shape modeling which will allow the acquisition of a digital scan of the tooth root canal shape at a high level of accuracy, without measurement artifacts, and with all the characteristic anatomical structures of the modeled canal. It is also desirable that the system for tooth root canal shape modeling allows the modeling of even thin unprepared canals without the need to perform additional preparations. It is additionally desirable that the system for tooth root canal shape modeling is a structurally simple solution, ensuring high operating reliability and increased durability. It is also desirable to provide a method for tooth root canal shape modeling which will allow a very precise and accurate digital scan of the tooth root canal shape used in further steps of manufacturing post-and- cores with the use of the CAD / CAM technology.

[0010] According to a first aspect of the invention, there is provided a system for tooth root canal shape modeling comprising an imaging device and a calibration stand, characterized in that the calibration stand comprises a body comprising two arms, with at least one reference element being arranged on the upper surface of the body, and a measurement insert comprising a canal part and a base part, wherein the body is detachably connected with the base part so that the canal part extends perpendicular to the upper surface of the body and substantially parallel to the reference element.

[0011] Preferably, the base part is detachably connected with the body with the use of a formfit connection.

[0012] Preferably, the form-fit connection is formed by a post extending from the base part and by a socket arranged on the upper surface of the body or by a post extending from the upper surface of the body and by a socket arranged in the base part.

[0013] Preferably, the post or the socket is located in the central region of the upper surface of the body, in the connection region of the two arms, and the reference element is located in the end region of one of the arms.

[0014] Preferably, the body is a cuboidal block extending horizontally.

[0015] Preferably, the body has two reference elements located on its upper surface, in the region of its opposite ends.

[0016] Preferably, the body has an additional third arm extending perpendicular to the first arm and to the second arm.

[0017] Preferably, the body has a third reference element located on its upper surface, in the end region of the third arm.

[0018] Preferably, the body has an additional fourth arm extending perpendicular to the first arm and to the second arm and opposite to the third arm.

[0019] Preferably, the body has a fourth reference element located on the upper surface, in the end region of the fourth arm.

[0020] Preferably, the reference element is a solid having a symmetry axis extending perpendicular to the upper surface of the body and substantially parallel to the canal part of the measurement insert. Preferably, the reference element is selected from a group comprising: a cone or a truncated cone, a cylinder, a prism with a polygonal base, a pyramid with a polygonal base and their combinations.

[0021] Preferably, the reference element has a height greater than the height of the measurement insert.

[0022] Preferably, the canal part of the measurement insert extends along an axis laterally shifted from the axis of the base part.

[0023] Preferably, the canal part of the measurement insert has a structured surface.

[0024] Preferably, the base part of the measurement insert has a bevel in the region adjacent to the canal part and / or in the region adjacent to the form-fit connection.

[0025] Preferably, the system additionally comprises a reference arch arranged above the upper surface of the body, at a distance greater than the height of the measurement insert and extending substantially parallel to the upper surface of the body, wherein the reference arch comprises at least one additional reference element.

[0026] Preferably, the reference arch is detachably connected with the body.

[0027] Preferably, the imaging device is an optical scanner.

[0028] According to the second aspect of the invention, there is provided a method for tooth root canal shape modeling comprising the following steps: a) impression compound is introduced into the tooth canal, and subsequently a measurement insert is introduced thereto, b) after the impression compound has set, the measurement insert is removed, c) the measurement insert with the set impression compound is scanned with the imaging device, characterized in that in step c) the measurement insert is scanned by means of the system for tooth root canal shape modeling as defined in the first aspect of the invention. Preferably, in step b), after the impression compound has set and before the measurement insert is removed, the base part of the measurement insert and at least one adjacent anatomical structure are scanned with the use of an intraoral imaging device.

[0029] The system for tooth root canal shape modeling according to this invention is used to obtain indirectly a scan of the shape of the inside of a broken tooth root in a spatial reference system relative to the adjacent teeth and to the occlusion. Owing to the design of the calibration stand, the system allows an accurate modeling of tooth root shapes together with various curvatures, recesses and the oval shape in the transverse plane. The system of the invention also allows work without the mechanical preparation of the tooth root (drilling, which weakens its structure), and only by means of removing e.g. the warm material (gutta percha) filling the root. Moreover, it allows work in a cofferdam, which reduces the risk of bacterial infection. The use of the calibration stand, which comprises the reference elements as defined in this invention, allows increased scanning accuracy in the case of narrow and longitudinal elements, such as a tooth root canal impression, by adding reference structures for the imaging device. On the other hand, the increased number of the reference elements and the addition of the reference arch with the additional reference elements further increases scanning accuracy, while reducing the risk of generating artifacts in digital models of scanned structures. Additionally, with the axis of the canal part being shifted from the axis of the base part, the asymmetry of the measurement insert allows the digital model obtained by means of the intraoral scan to be positioned with respect to the measurement insert located in the tooth canal. On the other hand, the use of the structured surface of the canal part allows an increased retention of the impression compound.

[0030] Importantly, the object of this invention is dedicated for prosthodontic works in which the post-and-core is manufactured in the CAD / CAM technology, and therefore it allows the use of any material suitable for machining, such as, without limitation, zirconium, gold, cobalt-chromium alloys, sintron, TRINIA, titanium or any other dentistry alloy. In comparison to classical post-and-core manufacturing methods, the use of this invention in the CAD / CAM process of manufacturing post-and-cores allows increased accuracy and fitting level regardless of the used material. Moreover, it is worth to be stressed that the object of the invention can not only serve to model the natural shape of the canal, but also ensure full control of this shape, e.g. when it is advantageous to change the cross-sectional shape to oval shape in order to prevent the possible rotation of the post-and-core in the canal. The object of the invention is thus not limited only to be used in modeling the shapes of unprepared canals, but - to the contrary - it allows the modeling of any anatomical teeth structures, as well as structures resulting from prior preparation, such as prepared canals.

[0031] The solution according to the present invention has been shown in the embodiments below and illustrated in the drawing, in which Fig. 1 is an axonometric view of the calibration stand according to one embodiment of the system for tooth root shape modeling, Fig. 2 is an axonometric view of the measurement insert shown in Fig. 1, Fig. 3 is an axonometric view of the body of the calibration stand shown in Fig. 1, Fig. 4 is a front view of the calibration stand according to another embodiment of the invention with the impression compound present on the canal part of the measurement insert, Fig. 5 is a digital model of the tooth root shape obtained with the system for tooth root shape modeling of this invention, Figs. 6A-K are axonometric views of non-limiting embodiments of the calibration stands of the system for tooth root shape modeling of this invention.

[0032] Example 1

[0033] An embodiment of the system for tooth root shape modeling according to this invention is shown in an axonometric view in Figs. 1 - 3. In general, the system for tooth root shape modeling comprises an imaging device and a calibration stand. In this embodiment, the imaging device is an optical scanner, but it is not a limitation to the scope of this invention, and in alternative embodiments it is possible to use other imaging devices, such as a laser scanner, acoustic scanner or a mechanical profilometer, on condition that they allow the recording of the digital model of the analyzed object. The type of the applied optical scanner is also not a limitation and depending on the application, it is possible to use for example UV, VIS, IR scanners with or without structured light beam.

[0034] A non-limiting embodiment of the system for tooth root shape modeling comprises a calibration stand which is arranged on a rotatable platform and an imaging device which is arranged in a circumferential position with the imaging beam aimed at the analyzed element. Alternatively, a fixed design of the calibration stand can be used with a circumferentially rotating imaging device or a plurality of imaging devices arranged circumferentially and covering the entire 3D surface of the analyzed object with the imaging beam.

[0035] The calibration stand shown in an axonometric view in Figs. 1 - 3 is a significant component of the system for tooth root shape modeling according to this invention. The calibration stand comprises a body 1, with two arms, i.e a first arm 7 and a second arm 8. In this embodiment shown in Figs. 1 - 3, the body 1 is cuboidal in shape and extends horizontally, i.e. it has a longer side which extends horizontally and a shorter side which extends vertically, wherein a flat upper surface of the body 1 is present.

[0036] It should be noted, however, that the shape of the body 1 is also not limited to the cuboidal shape shown in this embodiment and in alternative embodiments it can assume the shape of a different solid, on condition that the flat upper surface is present.

[0037] Going back to Figs. 1 - 3, there are two reference elements 2 arranged on the upper surface of the body, in the end regions of the first arm 7 and of the second arm 8, respectively. It should be here emphasized that in alternative embodiments it is possible to use a smaller or a greater number of reference elements 2, with at least one reference element 2 being required. Figs. 6A-C show an embodiment of the body 1 with one reference element 2 arranged in the region of one of the arms 7, 8.

[0038] As best visible in Fig. 1, a measurement insert 3 extends upwards from the upper surface of the body 1. The measurement insert 3 is detachably connected with the body 1 with the use of a form-fit connection 6. In this embodiment, the form-fit connection 6 is formed by a post 11 and a socket 12, complementary to each other and formed to fit loosely. On the other hand, the measurement insert 3 comprises a base part 5, with a narrow canal part 4 extending therefrom, dedicated to be introduced into the tooth root canal. Opposite to the canal part 4, the post 11 extends from the base part 5 and is received by the socket 12 formed in the central part of the upper surface of the body 1, in the connection region of the first arm 7 and the second arm 8. In an alternative embodiment, the form-fit connection 6 may be formed by complementary and fitting forms of other shapes, provided that the measurement insert 3 is securely mounted in the body 1 of the calibration stand. In yet another embodiment, the post 11 extends from the upper surface of the body 1 and is fitted with the socket 12 located in the base part 5, opposite to the canal part 4.

[0039] In one embodiment of the system for tooth root shape modeling, the canal part 4 of the measurement insert 3 extends along an axis laterally shifted from the axis of the base part 5. The lateral shift of the canal part 4 from the axis defining the axis of the base part 5 ensures additional feedback information on the geometry of the modeled shape during the scanning of the measurement insert 3 arranged inside the tooth root canal with the set impression compound. In yet another embodiment, the canal part 4 of the measurement insert 3 has a structured outer surface (for example notched, matted, roughened or knurled) for ensuring improved retention of the impression compound. In another preferred embodiment, the base part 5 of the measurement insert 3 has a bevel in the region adjacent to the canal part 4. The bevel (shown in Fig. 2), located adjacent to the canal part 4 of the measurement insert 3, is used to facilitate the orientation of the digital model of the measurement insert 3 after scanning (due to the non-symmetrical character of the base part 5) as well as to facilitate access to the anatomical structures of the patient for the scanning beam during the scanning with the use of the intraoral scanner with the measurement insert 3 introduced into the tooth root. Additionally, the base part 5 may be provided with an analogical bevel in the region adjacent to the formfit connection 6 for additionally facilitating the orientation of the digital model and access to the scanning beam.

[0040] Preferably, in the tooth root shape modeling system, the reference element 2 is in the form of a solid having a symmetry axis extending perpendicular to the upper surface of the body 1 and substantially parallel to the canal part 4 of the measurement insert 3. In the embodiment shown in Figs. 1 - 3, the reference elements 2 are in the form of two regular octagonal truncated pyramids arranged one over another in such a manner that they are connected with their bases. Both of the truncated octagonal pyramids of each reference element 2 share the vertical symmetry axis which is parallel to the symmetry axis of the canal part 4 of the measurement insert 3. On the upper surface of the two connected truncated pyramids, the reference element 2 arranged on the first arm 7 has a solid in the form of a regular hexagonal prism and the thus connected three solids form a complete reference element 2 according to this invention, arranged on the first arm 7. In turn, on the second arm 8, there is a square pyramid arranged on the upper surface of the two connected regular truncated pyramids. The thus connected three solids form a complete reference element 2 according to this invention, arranged on the second arm 8. In this embodiment, the height of the reference element 2 is greater than the height of the base part 5 of the measurement insert 3, and smaller than the height of the canal part 4 of the measurement insert 3, but in alternative embodiments the height of the reference element 2 can be greater than the height of the entire measurement insert 3 mounted in the body 1 of the calibration stand.

[0041] It is worth emphasizing that the shape of the reference element 2 is not limited to that shown in Figs. 1 - 3, and in alternative embodiments it is possible to use a reference element 2 having a different geometry, for example in the form of a solid having a symmetry axis extending perpendicular to the upper surface of the body 1 and substantially parallel to the canal part 4 of the measurement insert 3. The reference element 2 can thus assume a form of a cone or a truncated cone, a cylinder, a prism with a polygonal base, a pyramid with a polygonal base and their combinations. Non-limiting examples of alternative reference elements 2 are shown in Fig. 4 and in Figs. 6A-K, where in Fig. 4 the reference elements 2 are in the form two regular octagonal truncated pyramids arranged one over another in such a manner that they are connected with their bases, in Fig. 6A the reference element 2 is in the form of square-based pyramid, in Fig. 6B the reference element 2 is in the form of a cone, in Fig. 6C the reference element 2 is in the form of two cylinders arranged one over another, wherein the base of the upper cylinder has a smaller diameter and the two cylinders share the symmetry axis, in Fig. 6D the reference elements 2 are in the form of cylinders, in Fig. 6E the reference elements 2 are in the form of rectangular prisms arranged one over another, wherein the dimensions of the upper prism are smaller than the dimensions of the lower prism, in Fig. 6F the reference elements 2 are in the form of octagrammic prisms arranged one over another, wherein the base of the upper prism is smaller than the base of the lower prism, in Fig. 6G each reference element 2 is in the form of a different solid, wherein the first reference element 2 is in the form of an octagrammic pyramid, the second reference element 2 is in the form of two dodecagrammic prisms arranged one over another, wherein the dimensions of the base of the upper prism are smaller than the dimensions of the base of the lower prism, and the third reference element 2 is in the form of cross-shaped prisms arranged one over another, wherein the base of the upper prism is smaller than the base of the lower prism, in Fig. 6H the reference elements 2 are in the form of an octagrammic pyramid arranged over a truncated octagrammic pyramid, wherein the size of the base of each upper pyramid in each reference element 2 is different and greater than the size of the upper base of the lower truncated pyramid, in Fig. 61 each reference element 2 is in the form of a different solid, wherein the first reference element 2 is in the form of an octagrammic pyramid, the second reference element 2 is in the form of two octagrammic prisms arranged one over another wherein the base of the upper prism is smaller than the base of the lower prism, the third reference element 2 is in the form of an octagrammic prism and the fourth reference element 2 is in the form of an octagrammic pyramid arranged over a truncated octagrammic pyramid, in Fig. 6J the reference element 2 is in the form of rectangular prisms arranged one over another, wherein the dimensions of the base of the upper prism are smaller than the dimensions of the base of the lower prism, and in Fig. 6K each reference element 2 is in a different form, wherein the first reference element 2 is in the form of an octagrammic prism, the second reference element 2 is in the form of rectangular prisms arranged one over another, wherein the dimensions of the base of the upper prism are smaller than the dimensions of the base of the lower prism, the third reference element 2 is in the form of a cylinder arranged over a rectangular prism, and the fourth reference element 2 is in the form of a cross-shaped prism and a rectangular prism arranged one over another. In a further alternative embodiment, not shown in the figures, the reference element 2 can be in the form of an irregular solid, such as a solid resembling one of the adjacent teeth.

[0042] The system for tooth root shape modeling shown and described in detail above is used in the method for tooth root shape modeling. The method comprises a step in which: a) impression compound is introduced into the tooth canal, and subsequently a measurement insert 3 is introduced thereto, b) after the impression compound has set, the measurement insert 3 is removed, c) the measurement insert 3 with the set impression compound is scanned with the use of the imaging device after the measurement insert 3 had been connected to the calibration stand with the use of the form-fit connection 6.

[0043] Optionally, after the impression compound has set and before the measurement insert 3 is removed, the base part 5 of the measurement insert 3 and at least one adjacent anatomical structure are scanned with the use of an intraoral imaging device.

[0044] A detailed plan of the prosthodontic treatment can comprise the following steps:

[0045] 1. Root canal treatment of a tooth in a cofferdam (typically realized during the previous visit in the dental clinic).

[0046] 2. Scanning of the dentition and of the occlusion with the root protected with composite.

[0047] 3. Installation of a cofferdam, wherein the cofferdam is installed in such a manner that the treated tooth is located in the work (i.e. unprotected) space together with at least one tooth adjacent to the treated tooth.

[0048] 4. Removal of the protective composite and preparation of the inside of the tooth root.

[0049] 5. Scanning of the area exposed by the cofferdam (the broken tooth and at least one adjacent tooth).

[0050] 6. Application of the impression compound into the tooth root canal.

[0051] 7. Insertion of the measurement insert 3 into the tooth root together with the compound, wherein the canal part 4 is introduced into the tooth canal, and the base part 5 protrudes outside the tooth canal and is visible to the intraoral scanner.

[0052] 8. Scanning of the measurement insert 3, i.e. of its visible base part 5 together with the at least one adjacent tooth (and the anatomical structures exposed by the cofferdam).

[0053] 9. Removal of the measurement insert 3 and arranging it on the calibration stand with the use of the form-fit connection 6 (see Fig. 4, where the canal part 4 of the measurement insert 3 has a set impression compound corresponding in shape to the tooth root canal).

[0054] 10. Using the scanning device to scan the measurement insert 3 positioned on the calibration stand, wherein the result of scanning is the digital model of the inside of the canal together with the surrounding tissues (for example in the form of preserved tooth elements protracting above the gum and / or gum fragments).

[0055] 11. Sending the digital scans to the laboratory.

[0056] 12. Protecting the tooth again with the composite and removing the cofferdam.

[0057] 13. Designing and manufacturing the post-and-core in the laboratory. The technician positions the scans with respect to each other on the basis of the teeth adjacent to the broken tooth and of the measurement insert 3 present in different scans. The calibration stand is digitally removed from the design, as it only serves to scan the measurement insert 3 together with the impression compound.

[0058] 14. During the subsequent visit, the cementing of the post-and-core and starting the procedure of installing the prosthetic crown, wherein these actions are performed optionally in a cofferdam.

[0059] Example 2

[0060] The second embodiment of the system for tooth root shape modeling according to this invention is shown in an axonometric view in Fig. 6F.

[0061] The system for tooth root shape modeling has a structure similar to the structure of the system shown in the first embodiment, and therefore similar components will not be described again for the clarity of this description of the invention.

[0062] Unlike in the first embodiment, in the second embodiment the body 1 has an additional third arm 9 extending perpendicular to the first arm 7 and to the second arm 8 and a fourth arm 10 extending perpendicular to the first arm 7 and to the second arm 8 and opposite to the third arm 9. As a result, the body 1 is a structure resembling a cross from the top view. In alternative embodiments (not shown in the figures), the body 1 can comprise only three arms 7, 8, 9, forming a structure resembling the letter T in a top view.

[0063] As shown in Fig. 6F, the reference elements 2 are arranged on the first arm 7, on the second arm 8 and on the third arm 9, wherein each of the reference elements 2 assumes the shape of an identical solid. In alternative embodiments, the reference element 2 arranged on each arm 7, 8, 9, 10 can be different, as shown for example in Figs. 6G, H, I, K. An increase in the number of the arms and the reference elements 2 increases the accuracy of the scanning, limiting the number of artifacts generated during this process.

[0064] Example 3

[0065] The third embodiment of the system for tooth root shape modeling according to this invention is shown in an axonometric view in Fig. 6J.

[0066] The system for tooth root shape modeling has a structure similar to the structure of the system shown in the first embodiment, and therefore similar components will not be described again for the clarity of this description of the invention.

[0067] Unlike in the first embodiment, in the third embodiment the body 1 of the calibration stand further comprises a reference arch 13 arranged above the upper surface of the body 1, at a distance greater than the height of the measurement insert 3 and extending substantially parallel to the upper surface of the body 1. The reference arch 13 comprises at least one additional reference element 14. In this embodiment shown in Fig. 6J, there are four additional reference elements 14 in the form of cuboidal blocks protruding from the reference arch 13 upwards and downwards, towards the upper surface of the body 1. Analogically to the reference elements 2, the additional reference elements 14 are not limited to those shown in this embodiment, and in alternative embodiments it is possible to use different solids to build additional reference elements 14, for example such solids as those described in the context of the reference elements 2.

[0068] Additionally, in this embodiment the reference arch 13 is detachably connected to the body 1 and thus can be removed in some scanning cases. The detachable connection of the reference arch 13 to the body 1 can be provided with the use of technical means analogical to the form-fit connection 6 in the case of the detachable connection of the measurement insert 3 to the upper surface of the body 1.

[0069] Fig. 6K shows an alternative form of the third embodiment of the system for tooth root shape modeling, in which the body is in the form of a cross with four arms 7, 8, 9, 10 with different reference elements 2 arranged thereon. List of reference numerals:

[0070] 1 - body

[0071] 2 - reference element

[0072] 3 - measurement insert 4 - canal part of the measurement insert

[0073] 5 - base part of the measurement insert

[0074] 6 - form-fit connection

[0075] 7 - first arm

[0076] 8 - second arm 9 - third arm

[0077] 10 - fourth arm

[0078] 11 - post

[0079] 12 - socket

[0080] 13 - reference arch 14 - reference element

Claims

Claims1. A system for tooth root canal shape modeling comprising an imaging device and a calibration stand, characterized in that the calibration stand comprises a body (1) comprising two arms (7, 8), with at least one reference element (2) being arranged on the upper surface of the body (1), and a measurement insert (3) comprising a canal part (4) and a base (5) part, wherein the body (1) is detachably connected with the base part (5) so that the canal part (4) extends perpendicular to the upper surface of the body (1) and substantially parallel to the reference element (2).

2. The system according to claim 1, characterized in that the base part (5) is detachably connected with the body (1) with the use of a form-fit connection (6).

3. The system according to claim 2, characterized in that the form-fit connection (6) is formed by a post (11) extending from the base part (5) and by a socket (12) arranged on the upper surface of the body (1) or by a post (11) extending from the upper surface of the body (1) and by a socket (12) arranged in the base part (5).

4. The system according to claim 3, characterized in that the post (11) or the socket (12) is located in the central region of the upper surface of the body (1), in the connection region of the two arms (7, 8), and the reference element (2) is located in the end region of one of the arms (7, 8).

5. The system according to any of claims 1 - 4, characterized in that the body (1) is a cuboidal block extending horizontally.

6. The system according to any of claims 1 - 5, characterized in that the body (1) has two reference elements (2) located on its upper surface, in the region of its opposite ends.

7. The system according to any of claims 1 - 6, characterized in that the body (1) has an additional third arm (9) extending perpendicular to the first arm (7) and to the second arm (8).

8. The system according to claim 7 , characterized in that the body (1) has a third reference element (2) located on the upper surface, in the end region of the third arm (9).

9. The system according to claims 7 or 8, characterized in that the body (1) has an additional fourth arm (10) extending perpendicular to the first arm (7) and to the second arm (8) and opposite to the third arm (9).

10. The system according to claim 9, characterized in that the body (1) has a fourth reference element (2) located on the upper surface, in the end region of the fourth arm (10).

11. The system according to any of claims 1 - 10, characterized in that the reference element (2) is a solid having a symmetry axis extending perpendicular to the upper surface of the body (1) and substantially parallel to the canal part (4) of the measurement insert (3).

12. The system according to claim 11, characterized in that the reference element (2) is selected from a group comprising: a cone or a truncated cone, a cylinder, a prism with a polygonal base, a pyramid with a polygonal base and their combinations.

13. The system according to any of claims 1 - 12, characterized in that the reference element (2) has a height greater than the height of the measurement insert (3).

14. The system according to any of claims 1 - 13, characterized in that the canal part (4) of the measurement insert (3) extends along an axis laterally shifted from the axis of the base part (5).

15. The system according to any of claims 1 - 14, characterized in that the canal part(4) of the measurement insert (3) has a structured surface.

16. The system according to any of claims 1 - 15, characterized in that the base part(5) of the measurement insert (3) has a bevel in the region adjacent to the canal part (4) and / or in the region adjacent to the form-fit connection (6).

17. The system according to any of claims 1 - 16, characterized in that it additionally comprises a reference arch (13) arranged above the upper surface of the body (1), at a distance greater than the height of the measurement insert (3) and extending substantially parallel to the upper surface of the body (1), wherein the reference arch (13) comprises at least one additional reference element (14).

18. The system according to claim 17, characterized in that the reference arch (13) is detachably connected to the body (1).

19. The system according to any of claims 1 - 18, characterized in that the imaging device is an optical scanner.

20. A method for tooth root canal shape modeling comprising the following steps: a) impression compound is introduced into the tooth canal, and subsequently a measurement insert is introduced thereto, b) after the impression compound has set, the measurement insert is removed, c) the measurement insert with the set impression compound is scanned with the imaging device, characterized in that in step c) the measurement insert is scanned by means of the system for tooth root canal shape modeling as defined in any of claims 1 - 19.

21. The method according to claim 20, characterized in that in step b), after the impression compound has set and before the measurement insert is removed, the base part (5) of the measurement insert (3) and at least one adjacent anatomical structure are scanned with the use of an intraoral imaging device.

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