Dental optical impression root post and methods relating thereto

Abstract

Dental root post (1) for taking an intraoral optical impression, comprising a body (2) intended to be received in a dental root and a head (3) forming a plurality of polygonal facets (11-18), which are preferably asymmetrical with respect to each other. Method for constructing a virtual model of such a post and methods for using such a post and / or such a model. Figure for abstract: Fig. 1

Description

Title of the invention: Optical impression dental root post and methods relating thereto Technical field

[0001] The invention relates to the field of reconstructive dental medicine.

[0002] The invention relates more specifically to a dental root post for optical impression taking, a method of constructing a virtual model of such a post, as well as methods of using such a post and such a model. State of the prior art

[0003] In the field of dentistry, it is common to reconstruct decayed teeth using dental prostheses such as prosthetic crowns.

[0004] The manufacture and installation of a coronal infrastructure requires first taking an impression of the internal volume of the root of the tooth concerned.

[0005] Traditionally, the impression is taken by molding an elastomeric material recording the dental volumes including those of the roots using pins intended for analog impressions.

[0006] The deployment of digital tools has made it possible to develop optical impression-taking techniques, by acquiring images using intraoral scanners.

[0007] Optical impression techniques provide satisfactory results in implantology but generally do not allow a correct impression of the root volume of a tooth to be obtained.

[0008] Known optical impression root posts typically comprise a body intended to be inserted into the root of a tooth and a scanning element, known as a "scan post", which is fixed to the body so as to be able to be detected by the scanner.

[0009] The accuracy of root volume impressions obtained using conventional scanning elements is generally unsatisfactory or even random, in terms of angulation and depth. Statement of the invention

[0010] The invention aims to overcome all or part of the drawbacks associated with conventional impression-taking techniques.

[0011] To this end, the invention relates to a dental root post for taking an intraoral optical impression, comprising: - a body intended to be received in a dental root, - a head forming a plurality of polygonal facets.

[0012] Advantageously, the facets may be asymmetrical with respect to each other.

[0013] More generally, the geometry of the facets can be defined in such a way that views of the head each taken from a respective viewing angle are each unique, at least allowing the actual arrangement of the tenon to be determined precisely and reliably during a digital reconstruction phase.

[0014] In one embodiment, one or more of said facets, in a non-limiting manner all the facets, each form an irregular polygon.

[0015] In one embodiment, one or more of said facets, in a non-limiting manner all the facets, each form a triangle.

[0016] Such geometry makes it possible to simplify the design and / or manufacture of the tenon.

[0017] Preferably, all or part of said facets are parallel to fictitious planes respective ones which are secant to each other.

[0018] In one embodiment, the head forms: - edges each delimiting one or more of said facets, - points of intersection of said edges.

[0019] In a non-limiting manner, each of said points may correspond to a point of intersection of two of said edges with each other, or of one of said edges with a part of the tenon, for example its body.

[0020] In one embodiment, the intersection points form one or more groups, the intersection points of each of said groups forming vertices of a respective polygon.

[0021] Such groups of points, and / or the polygons they define, may delimit different stages of the head. Thus, the head may comprise a number N of stages, which may for example be stacked on top of each other, so that each of the stages is delimited on the one hand by the points and / or the corresponding polygon of one of the groups and, on the other hand, by the points and / or the corresponding polygon of another of said groups. Generally, N may be greater than or equal to two, for example equal to three.

[0022] The polygons defined by these different groups can preferably be oblique to each other.

[0023] In one embodiment, for the polygon defined by each of said groups, this polygon comprises edges each forming a respective one of said edges.

[0024] In one embodiment, the intersection points of each of said groups are spaced from the intersection points of the other groups along a direction defining an axis of the tenon.

[0025] The tenon is preferably a single piece. In other words, the body and the head of the tenon can be manufactured from a single piece.

[0026] The tenon may comprise at least one material chosen from a list including: - a metal, for example titanium, - a metal alloy, for example stainless steel, - a plastic, for example a polyetheretherketone or a polyertacetal.

[0027] Of course, the material is preferably chosen according to the use of the post. For example, a post intended for single use can be made of plastic. A post intended to be used several times can be made of titanium or 316L surgical steel, for example.

[0028] Generally speaking, the invention and in particular the geometry of the head of a tenon as defined above make it possible to improve the accuracy of the estimation of the inclination and the insertion depth of the tenon in the context of a digital reconstruction. Compared to conventional techniques, the invention makes it possible to improve the reliability and accuracy of such an estimation.

[0029] The invention thus makes it possible to produce precise and reliable optical impressions and, consequently, better adapted dental infrastructures.

[0030] According to another aspect, the invention also relates to a method for constructing a virtual model of a tenon as defined above.

[0031] This construction method generally comprises a determination of data representative of the tenon, this data forming said virtual model.

[0032] In one embodiment, the determining step comprises generating data representative of edges and / or points of the head of the tenon.

[0033] These data are preferably generated so as to respect one or more parameters which can be chosen from a list including, in a non-limiting manner, a number of edges, an edge length, an angle between edges, a number of points, a distance between edges and / or points, a number of facets, a facet geometry and a facet surface.

[0034] The construction method may comprise, in particular after the step of determining the data, storing said data in a database.

[0035] According to another aspect, the invention also relates to a method for taking an intraoral optical impression of a dental arch of an individual having a tooth receiving the body of a post as defined above.

[0036] This optical impression taking method may comprise an acquisition of one or more images of the head of the post and of at least a portion of the dental arch.

[0037] This acquisition of hnage(s) can be carried out using an optical sensor, for example a conventional intraoral scanner.

[0038] In a manner known per se, an optical impression allows a practitioner to obtain a three-dimensional image of one or more teeth from which a prosthesis can be designed and manufactured with computer assistance.

[0039] According to another aspect, the invention also relates to a method for determining a position of the body of a post as defined above, from a three-dimensional oral image.

[0040] This three-dimensional oral image can typically be reconstructed from one or more images acquired using an optical impression-taking method as defined above.

[0041] The method for determining the position of the body of the post preferably comprises a step of superimposing a three-dimensional image of said post with said oral image.

[0042] Without limitation, the three-dimensional image of the post may be formed from a virtual model of the post which may be constructed in the manner indicated above.

[0043] Other advantages and characteristics of the invention will appear on reading the detailed, non-limiting description which follows. Brief description of the drawings

[0044] The following detailed description refers to the accompanying drawings in which: - [Fig.l] is a view, from a first viewing angle, of an optical impression dental root post in accordance with the invention; - [Fig.2] is a view, from a second angle, of part of the tenon of [Fig.l]; - [Fig.3] is a view, from a third angle, of part of the tenon of [Fig.l]; - [Fig.4] is a view, from a fourth angle, of part of the tenon of [Fig.l]; - [Fig.5] is a view, from a fifth angle, of part of the tenon of [Fig.l]; - [Fig.6] is a view, from a sixth angle, of part of the tenon of [Fig.l]; - [Fig.7] is a view, from a seventh angle, of part of the tenon of [Fig.l]; - [Fig.8] is a view, from an eighth angle, of part of the tenon of [Fig.l]; - [Fig.9] is a view, from a ninth angle, of part of the tenon of [Fig.l]. Detailed description of embodiments

[0045] [Fig.l] shows tenon 1 according to a non-limiting embodiment of the invention.

[0046] The post 1 of [Fig.l] is a dental root post extending along an axis A1 and comprising a lower part 2 called “body” and an upper part 3 called “head”.

[0047] The body 2, also called the “tail”, of the post 1 is intended to be received in a prepared dental root, that is to say one whose dentino-pulpal complex has been replaced by a filling material and then secondarily shaped using drills specific to the post.

[0048] The body 2 of the tenon 1 has a conventional geometry in this example.

[0049] In this example, the body 2 extends along the axis Al, forming a part 2A called proximal, which is connected to the head 3 of the tenon 1, and a part 2B called distal which extends axially opposite the head 3. The proximal part 2A is generally cylindrical, while the distal part 2B is generally conical.

[0050] In a non-limiting manner, the proximal part 2A and the distal part 2B each have a smooth surface.

[0051] For information purposes, the body 2 of the tenon 1 has in this example a total length XI of 21 mm, its proximal part 2A has a length X2 of 12.3 mm and a diameter of 1.8 mm, and its distal part 2B has a length X3 of 8.7 mm and a diameter of 0.6 mm at its end opposite the proximal part 2A.

[0052] Concerning the head 3 of the post 1, this is intended to be detected by an image acquisition device during an intraoral optical impression (see further below). The head 3 is also called a “scanning head”.

[0053] In this non-limiting example, the tenon 1 is a single piece, its body 2 and its head 3 being manufactured in a single piece by stereolithography from a digital model, in a plastic material of the polyetheretherketone type.

[0054] With reference to figures 1 to 9, the head 3 of the tenon 1 comprises a plurality of facets, referenced 11 to 33, that is to say a plurality of surface elements which are separated from each other by edges.

[0055] In this example, the facets are planar.

[0056] In a non-limiting manner, each of the facets formed by the head 3 is delimited by edges giving each of these facets a polygonal shape, in this case triangular.

[0057] In this example, the facets 11 to 32 are asymmetrical with respect to each other, that is to say that they are each delimited by a combination of edges having lengths and forming angles between them which are specific to each of these facets.

[0058] In a non-limiting manner, each of the facets 11 to 32 forms a polygon, in this example a triangle, which is irregular, that is to say whose sides do not all have the same length.

[0059] The head 3 of the tenon 1 thus comprises a plurality of edges each delimiting one or more of said facets, as well as points of intersection of these edges.

[0060] In the embodiment of Figures 1 to 9, the majority of the edges each delimit two respective adjacent facets. For example, one of the edges delimits both facets 12 and 13 visible in [Fig.l].

[0061] In this example, some of said intersection points are each formed by the intersection of one of the edges of the head 3 with a surface of the body 2 of the tenon 1. For example, with reference to [Fig. 1], intersection points are formed by the intersection of edges, which delimit facets 33, with the body 2 of the tenon 1. Other intersection points of the head 3 are in this example each formed by the intersection of at least two respective edges of the head 3. For example, with reference to [Fig. 1], a point P2 is formed by the intersection, in particular, of the edge delimiting the facets 12 and 13 with the edge delimiting the surfaces 13 and 14.

[0062] In this example, head 3 comprises several stages delimited from each other by groups of intersection points.

[0063] In this example, a first group comprises points referred to by the reference PO in [Fig. 1], these points corresponding to points of intersection of edges delimiting the facets 33 with the body 2 of the tenon 1. A second group comprises points referred to by the reference PI in [Fig. 1], these points corresponding to points of intersection of edges delimiting the facets 33 with edges delimiting the facets 14-18, 21-25 and 28-32. With reference to Figures 1 to 9, a third group comprises the points referenced P2-P4 and a fourth group comprises the points referenced P5-P7.

[0064] In a non-limiting manner, the points PO of the first group belong in this example to a circle formed by a surface of the body 2 of the tenon 1.

[0065] In this example, for each of the other groups of points, the points of the group form vertices of a respective polygon. More particularly, the points P1 of the second group form in this example the vertices of a first triangle as well as points belonging to the edges of this first triangle, the points P2-P4 of the third group form the vertices of a second triangle whose edges constitute the edges delimiting respectively the facets 13 and 14, the facets 20 and 21 and the facets 27 and 28, and the points P5-P7 of the fourth group form the vertices of a third triangle whose edges constitute the edges delimiting together the facet 11.

[0066] In this example, the first, second, and third triangles extend in respective planes that are oblique to each other.

[0067] Furthermore, the points of each of the aforementioned groups are spaced from the points of each of the other groups along the axis Al of the tenon 1, thus defining a head 3 provided in this example with three stacked stages along Al.

[0068] In this example, a first of these stages is delimited on either side by the first and second groups of points, this first stage forming the facets referenced 33. A second of these stages is delimited on either side by the second and third groups of points, this second stage forming the facets referenced 14-18, 21-25 and 28-32. A third of these stages is delimited on either side by the third and fourth groups of points, this third stage forming the facets referenced 12, 13, 19, 20, 26 and 27.

[0069] A design method will now be described for constructing a virtual model of a tenon in accordance with the invention.

[0070] This method can be implemented to construct a virtual model of a tenon whose geometry corresponds to that of the tenon 1 described above with reference to Figures 1 to 9, or of a tenon having other geometries in accordance with the invention not shown in the present document. The following description is made with reference to the tenon 1 of Figures 1 to 9 and applies by analogy to any other tenon in accordance with the invention.

[0071] The design method described below is implemented by computer.

[0072] In this particular example, which is in no way limiting, a three-dimensional spatial reference frame is formed on the one hand by a reference axis corresponding to the axis A1 of the tenon 1 and, on the other hand, by a reference circle which passes through a plane perpendicular to the reference axis and which corresponds to said circle formed by the body 2 of the tenon 1.

[0073] The following description is primarily intended to indicate examples of non-limiting conditions that can be met by a point cloud generated according to a method in accordance with the invention. Of course, numerous algorithmic principles can be implemented to do this. In particular, the following non-limiting steps can be carried out simultaneously or in a different order.

[0074] In a first step, twelve first points are generated on the reference circle, equidistant from each other. The first points thus generated form in this example the points PO of said first group.

[0075] For the following steps, axial reference planes passing through the reference axis and which are oblique to each other are defined.

[0076] In a second step, twelve second points are generated at positions which are defined so that: - the second points pass through a plane parallel to a first of said axial reference planes, this first axial plane being perpendicular to the reference axis, - the barycenter of a first triangle whose vertices are formed by three of said second points is spaced, along the reference axis, from the plane passing through the reference circle at a distance within a predetermined range, - the barycenter of the first triangle passes through the reference axis, - the ratio between the surface formed by the first triangle and the surface formed by the reference circle is within a predetermined range.

[0077] The second points thus generated form in this example the points PI of the second group and the sides of said first triangle thus form edges each delimiting one of the facets 33 of the first stage and one of the facets of the second stage.

[0078] In a third step, three third points are generated at positions which are randomly defined, using any suitable software function, so that: - the third points pass through a plane which has, with respect to a second of said axial reference planes, an angle within a predetermined range, - the barycenter of a second triangle whose vertices are formed by the third points is spaced, along the reference axis, from the barycenter of said first triangle by a distance within a predetermined range, - the barycenter of the second triangle is spaced from the reference axis by a distance within a predetermined range, - the length of each of the sides of the second triangle is within a predetermined range and is different for each of these sides, - the angle formed by each of the pairs of sides of the second triangle is within a predetermined range, - the ratio between the surface area formed by the second triangle and the surface area formed by said first triangle is within a predetermined range.

[0079] The third points thus generated form in this example the points P2-P4 of the third group and the sides of said second triangle thus form the edges delimiting the facets of the second stage and those of the third stage.

[0080] In a fourth step, three fourth points are generated at positions which are randomly defined, using any suitable software function, so that: - the fourth points pass through a plane which has, with respect to a third of said axial reference planes, an angle within a predetermined range, - the barycenter of a third triangle whose vertices are formed by the fourth points is spaced, along the reference axis, from the barycenter of said second triangle by a distance within a predetermined range, - the barycenter of the third triangle is spaced from the reference axis by a distance within a predetermined range, - the length of each of the sides of the third triangle is within a predetermined range and is different for each of these sides, the length of each of the sides of the third triangle further preferably being different from the length of each of the sides of said second triangle, - the angle formed by each of the pairs of sides of the third triangle is within a predetermined range, - the ratio between the surface area formed by the third triangle and the surface area formed by said second triangle is within a predetermined range.

[0081] The fourth points thus generated form in this example the points P5-P7 of the fourth group and the sides of said third triangle thus form the edges delimiting the facet 11.

[0082] Depending on the algorithms and / or calculation methods used, one or more of the conditions indicated above may be deleted and / or replaced by other conditions, additional conditions may of course be applied.

[0083] Such a method makes it possible to form data which are in this example representative of intersection points and edges of the head of the tenon.

[0084] These data, which can of course include in a complementary manner data representative of the body of the tenon, thus form a virtual model of the tenon 1.

[0085] The method can be implemented to generate several data sets which each correspond to a respective virtual model of the tenon.

[0086] By having several virtual models thus generated, it is possible to select one of these models according to different criteria which may relate, in a non-limiting manner, to the ease of manufacturing of the tenon and / or to a principle of univocity.

[0087] Concerning for example the criterion of ease of manufacture, parameters such as the angles each formed by two adjacent facets of the head of the tenon can be taken into account. For example, a model can be selected if the angle formed by any pair of adjacent facets of the head of the tenon is less than a predetermined angle, beyond which manufacturing constraints would not allow, for example, the tenon to be machined, depending of course on the manufacturing technique chosen.

[0088] Optionally, the design method may comprise a step of manually adjusting the position of one or more of said points and / or one or more of said edges, in order for example to comply with manufacturing constraints.

[0089] The aforementioned principle of univocity can relate to the univocity of views of the head of the tenon from several viewing angles.

[0090] A univocity test can be implemented, in particular by computer, for example so as to verify that the projection onto different planes of intersection points which are visible according to different corresponding viewing angles results in a spatial distribution of the points thus projected which is different from one plane to another.

[0091] For another example, a univocity test may comprise a step of comparing the facets with each other when they are projected and superimposed in the same plane. In a non-limiting manner, a univocity criterion may for example be considered respected if the distance between each pair of corresponding vertices of two respective facets is greater than a predetermined value.

[0092] The data thus selected - or, in the absence of selection, the data generated using the design method - are stored in a database.

[0093] In this non-limiting example, the database takes the form of an “STL” format file which thus contains a virtual model of the tenon.

[0094] The file can be transmitted to stereolithography software in order to manufacture the post based on the virtual model contained in the file.

[0095] A post according to the invention, for example such as that described above, can be used to make an optical impression of the root of a tooth that one wishes to restore with a prosthetic crown, within the framework of a digital reconstruction of a dental arch, or of a part of the arch, with a view to designing and manufacturing said prosthesis.

[0096] In a manner known per se, the impression can be taken using an intraoral scanner moved into the individual's mouth, after having placed the impression post in the tooth concerned. Such a scanner thus makes it possible to acquire images of the dental arch and the head of the post, which of course extends outside the tooth.

[0097] During digital reconstruction, the images thus acquired make it possible to form a three-dimensional image of all or part of the corresponding dental arch, as well as the head of the post.

[0098] In this non-limiting example, the reconstruction software is configured to allow a superposition, on the aforementioned three-dimensional image, of a three-dimensional image of the impression post, for example on the basis of the virtual model of the post contained in the aforementioned file.

[0099] The superposition of these images makes it possible to calculate the precise arrangement of the body of the impression post in relation to the dental arch and, consequently, to precisely determine the geometry of the prosthesis to be manufactured.

[0100] The invention is of course not limited to the embodiment of figures 1 to 9 and covers all variants in accordance with the claims.

[0101] For example, the body of the tenon may have another geometry, for example entirely cylindrical, and / or have a textured, non-smooth surface.

[0102] For another example, the body and the head of the tenon can be manufactured separately and then assembled with each other. Furthermore, the tenon can be manufactured using any technique, for example by additive manufacturing and / or by machining, using many types of materials.

[0103] Regarding the head of the tenon, this may have various geometries. For example, one or more of the facets formed by the head may have one or more curvatures, for example a concave or convex surface.

[0104] In alternative embodiments, the head may form non-triangular polygonal facets, for example one or more quadrilateral and / or pentagonal facets, etc. More generally, the head may form facets each having a polygonal shape having a number of sides greater than or equal to three, the number of sides possibly being different from one facet to another. Of course, the number of points and / or edges and / or groups of points and / or stages may also be different from the example of Figures 1 to 9.

Claims

Claims

1. Dental root post (1) for taking an intraoral optical impression, comprising: - a body (2) intended to be received in a dental root, - a scanning head (3) forming a plurality of polygonal facets (11-32) which are asymmetrical with respect to each other.

2. A tenon (1) according to claim 1, wherein one or more of said facets (11-32) each form an irregular polygon and / or a triangle.

3. Tenon (1) according to claim 1 or 2, in which the head (3) forms: - edges each delimiting one or more of said faces (11-32), - points of intersection (P1-P7) of said edges.

4. Tenon (1) according to claim 3, wherein the intersection points (P1-P7) form one or more groups, the intersection points (PI; P2-P4; P5-P7) of each of said groups forming vertices of a respective polygon, the polygons defined by these different groups preferably being oblique to each other.

5. Tenon (1) according to claim 4, wherein: - for the polygon defined by each of said groups, this polygon comprises edges each forming a respective one of said edges, and / or - the intersection points (PI; P2-P4; P5-P7) of each of said groups are spaced from the intersection points of the other groups along a direction defining an axis (Al) of the tenon (1).

6. Method for constructing a virtual model of a tenon (1) according to any one of claims 1 to 5, comprising: - determining data representative of the tenon (1), these data forming said virtual model, - storing said data in a database.

7. Method according to claim 6, in which the determining step comprises a generation of data representative of edges and / or points of the head (3) of the tenon (1), so as to respect one or more parameters which can be chosen from a list including a number of edges, an edge length, an angle between edges, a number of points, a distance between edges and / or points, a number of facets, a facet geometry and a facet surface.

8. Method for taking an intraoral optical impression of a dental arch of an individual having a tooth receiving the body (2) of a post (1) according to any one of claims 1 to 5, the method comprising an acquisition using an optical sensor of one or more images of the head (3) of the post (1) and of at least part of the dental arch.

9. Method for determining a position of the body (2) of a post (1) according to any one of claims 1 to 5 from a three-dimensional oral image reconstructed from one or more images acquired using an optical impression-taking method according to claim 8, this method preferably comprising a step of superimposing a three-dimensional image of said post (1) with said oral image.

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