DENTAL SHADE MEASURING DEVICE

Abstract

The object of the invention is a dental shade measuring device (1) comprising a housing (11), a handle (10) and a measuring head (20), said device being characterized in that said measuring head (20) comprises: - a hollow body (40) extending along a longitudinal axis (46), said hollow body comprising a proximal end (48) and a distal end angled (49) with respect to the longitudinal axis (46), said distal end (49) being provided with a removable tip (26) intended to come into contact with an analysis surface of a tooth; - at least one light source and image acquisition means attached to the hollow body (40), said hollow body being capable of transmitting the light from said light source from the proximal end to the distal end;and in that said apparatus includes an orientation assembly allowing the proximal end (48) of the hollow body to be mounted in the housing (11) so that the measuring head (20) occupies different angular positions relative to the housing (11).

Description

The present invention relates to a dental shade measuring device intended for use by dental surgeons and dental prosthesis manufacturing laboratories. Tooth shade refers to a set of tooth characteristics that aim to represent the tooth's appearance as accurately as possible. Tooth shade thus corresponds to the color of the tooth, that is, its brightness, saturation, and hue, but can also incorporate any parameter that affects the tooth's appearance, such as its translucency or transparency, or its surface texture. When making a dental prosthesis, it is necessary that this prosthesis matches the colors of the neighboring teeth or as close as possible in order to go unnoticed in the patient's mouth. According to a known technique, a dentist can visually assess the shade of a tooth. The dentist takes a shade guide for the dental prosthesis by comparing the patient's tooth to reference teeth on a shade guide. The resulting shades are then provided to a dental technician to help them choose the appropriate paste mixtures for fabricating the prosthesis. However, this measurement technique is not very reliable. The assessment of tooth shade is subjective and can vary from one practitioner to another due to the eye's perception mechanism. Furthermore, this measurement is influenced by environmental factors such as lighting conditions. To eliminate errors in practitioner perception, a more objective evaluation can be performed using a spectral analysis device that exposes a tooth to a beam of light. Such a device comprises a handle and a measuring head that comes into contact with the tooth being measured. The measuring head is connected to the transmitting and receiving means via a bundle of optical fibers. The handle includes a light source, such as light-emitting diodes (LEDs), and the measuring head includes light sensors. However, this device only allows for spot measurements on the tooth. In another embodiment, an imaging device can be used to map the tooth. The captured image is then subjected to image processing, such as automatic segmentation, to determine a set of tooth characteristics. Such an imaging device includes a measuring head and a handle. The head comprises at least one image sensor, an optical system, and an LED lighting system to illuminate the imaging area. Although it allows for two-dimensional measurement, this device has a relatively bulky measuring head. Another drawback of these devices is that the measuring head remains fixed relative to the handle. Consequently, their use is limited to the anterior portion of the patient's dental arch. The present invention also aims to remedy the disadvantages of the prior art, by proposing a device with a very compact measuring head which allows for two-dimensional analysis while having access to all the teeth in the mouth. To this end, the present invention relates to a dental shade measuring device comprising a housing, a handle and a measuring head, said device being characterized in that said measuring head comprises: - a hollow body extending along a longitudinal axis, said hollow body comprising a proximal end, a distal end bent with respect to the longitudinal axis, said distal end being fitted with a removable tip intended to come into contact with an analysis surface of a tooth; - at least one light source and image acquisition means attached to the hollow body, said hollow body being capable of transmitting light from said light source from the proximal end to the distal end; and in that said apparatus includes an orientation assembly allowing the proximal end of the hollow body to be mounted in the housing so that the measuring head occupies different angular positions relative to the housing. According to one embodiment of the invention, the orientation assembly comprises at least one first half-shell adapted to be assembled to a second half-shell to form a hollow shell delimiting a cavity configured to receive said proximal end, said cavity having on its inner surface a radially projecting surface intended to cooperate with a plurality of housings having a shape 3 complementary formed on the outer surface of the proximal end to ensure the different angular positions of the measuring head relative to the housing. Advantageously, the orientation assembly includes a locking means to lock the measuring head in a defined angular position relative to the housing. According to a particularly advantageous embodiment, said hollow body consists of an optical guide surrounded by an overmolding comprising a set of fastening motifs. Preferably, said pattern set includes a clip pattern formed on the tip of the distal end of the hollow body to secure the tip. Preferably, said pattern assembly includes an annular shoulder forming an axial stop for the hollow body when the proximal end is mounted in said orientation assembly (50). According to a preferred embodiment of the invention, said at least one light source is fixed to the tip of the proximal end of the hollow body and said image acquisition means are fixed to the tip of the distal end of the hollow body. According to this embodiment, it includes a cable extending in the hollow body from the proximal end to the distal end to transmit an image from the distal end to the proximal end. According to one embodiment of the invention, said image acquisition means comprise a sensor and an optical system. Preferably, said at least one light source comprises at least one white light-emitting diode (LED) and light-emitting diodes (LEDs) whose wavelengths vary between 448 and 630 nm, said LEDs being fixed on a support. Advantageously, the said support includes a data processing unit and an LED control board. Preferably, the optical system includes a lens and at least one polarizing filter. According to one embodiment of the invention, the tip comprises a distal end intended to come into contact with the analysis surface of the tooth and a proximal end, said proximal end being separated from said distal end by a predefined distance corresponding to a working distance for image acquisition. Advantageously, the tip includes a color reference surface. Other features and advantages of the invention will become apparent from the following description of particular embodiments of the invention, given by way of non-limiting examples, with reference to the accompanying drawings, in which: - Figure 1 is a schematic perspective view of a color matching device according to one embodiment of the invention; - Figure 2 is an exploded perspective view of the measuring head of the device in Figure 1; - Figure 3 is a cross-sectional view from below of the casing of the device in Figure 1; - Figure 4A is a perspective view of the optical guide of the measuring head and Figure 4B is a perspective view of the optical guide with an overmolding; - Figure 5A illustrates a perspective view of the bent distal end of the hollow body, the tip of the distal end being equipped with image acquisition means; - Figure 5B illustrates a perspective view of the tip of the measuring head; - Figure 5C illustrates a perspective view of the tip fixed to the end of the bent distal end of the hollow body; - Figure 6 is a view of the measuring head of Figure 2 in an assembled configuration; - Figure 7 is a cross-sectional view of the proximal end of the measuring head held between two half-shells of the orientation assembly of the device. Figure 1 shows a measuring device for acquiring a color image of a tooth according to the invention, or spectral data of a tooth. These measurements allow for a complete and precise mapping of the variations in the different characteristics of the tooth. In particular, this mapping makes it possible to determine the tooth shade for the purpose of fabricating a dental prosthesis. This device includes a grippable handle 10 surmounted by a housing 11, one end of the housing 11 being equipped with a measuring head 20 for acquiring spectral data or images. According to one embodiment, the housing 11 has a substantially parallelepiped shape with an upper face 14 comprising a display 15 which allows to indicate in real time the data relating to the analyzed tooth coming from the measuring head 20. This data can then be transmitted to the user's computer system via Wi-Fi connection or via a USB connection to be processed by a computing unit. According to a particularly advantageous embodiment, the calculation unit is integrated directly into the housing 11 which allows the shade map of the analyzed tooth to be displayed. In one embodiment, the device includes a base 17 for placing the device on a flat surface. This base 17 also includes a USB cable 13 for data transfer. Furthermore, the handle 10 includes a compartment for a battery. This battery can be recharged, while the device is placed on its base, via a USB connection or via a charger connected to mains power. The grippable handle 10 also includes an activation button 12 for the measuring head. According to an embodiment illustrated in Figures 1 to 4, the measuring head 20 comprises a hollow body 40 oriented along a longitudinal axis 46. This hollow body includes a proximal end 48 mounted on the housing 11 and an angled distal end 49 equipped with a removable tip 26 for contacting an analysis surface of a tooth. The hollow body 40 also includes a passage 29 extending from the proximal end 48 to the distal end 49. The tip 48B of the proximal end 48 and the tip 49B of the distal end 49 are open. The measuring head 20 includes at least one light source 21 and image acquisition means, attached to the hollow body 40. According to a preferred embodiment of the invention, at least one light source is fixed to the end 48B of the proximal end 48 of the body 40, and the image acquisition means are fixed to the end 49B of the distal end 49 of the body 40. The latter allows the illumination light from the light source 21 to be transmitted from the proximal end 48 of the body to the distal end 49 of the body to illuminate the analysis surface of the tooth. The device further includes a data transmission cable 28 extending through the passage 29 of the body from the proximal end 48 of the body to the distal end 49 to transmit at least one image from the end 6 distal to the proximal end. This cable connects, in particular, the acquisition means to a data processing unit. According to one embodiment, the hollow body 40 consists of an optical guide 41 allowing the illumination light emitted by the light source to be guided towards a surface of the tooth, surrounded by an overmolding 42. According to an important feature, the device includes an orientation assembly 50 that allows the proximal end 48 of the hollow body 40 to be connected to the housing 11 so that the measuring head 20 occupies different angular positions relative to the housing. This specific arrangement provides the device of the present invention with an additional degree of freedom to facilitate access to the teeth of both dental arches. Furthermore, the ability to orient the measuring head without changing the position and orientation of the handle 10 relative to the tooth's analysis surface improves the user's experience with the device. The axis XX' of the distal end 49 of the hollow body 40 is preferably angled at an angle α relative to the longitudinal axis 46 of the body 40 to facilitate access of the measuring head to the teeth located in the posterior part of both dental arches. This angle is between 10 and 60°. It is preferably equal to 45°. The cooperation between the angled distal end 49 of the hollow body 40 and the different angular positions allows the tip 26 to be positioned so that the longitudinal axis XX' of the tip 26 is always perpendicular to the analysis surface of the tooth. The orientation assembly 50 comprises a first half-shell 51 and a second half-shell 52, the two half-shells being assembled to form a hollow shell delimiting a cavity 53 around the longitudinal axis 46. The two half-shells 51, 52 are held assembled by known fastening means 61, 62. The proximal end 48 of the hollow body 40 is received in the cavity 53. One of the two half-shells 52 includes a radially projecting surface 56 intended to cooperate with a plurality of housings having a complementary shape, formed on an external surface of the proximal end 48 of the hollow body 40 to ensure the different angular positions of the measuring head 20 relative to the housing 11. As illustrated in Figure 7, the proximal end 48, which has a substantially circular cross-section, is housed in the cavity 53 formed by the two half-shells 51, 52. The proximal end 48 has on its outer surface a series of seven numbered recesses, 57.1 to 57.7. These recesses are positioned to place the measuring head in various angular positions between 0 and 270°. The recesses are distributed so that the angular interval between any two positions is 45°. In Figure 7, the measuring head 20 is oriented to an angular position in which the protruding surface 56 is received in the recess 57.1, corresponding, for example, to a reference angular position of 0°. The measuring head 20 is then oriented relative to this reference angular position. The radially projecting surface, intended to cooperate with one of the housings 57, is formed by a ball screw 55 received in a housing 54 made in the wall of one of the half-shells 52 of the orientation assembly. This ball screw 55 includes, at one end oriented towards the interior of the cavity 53, a ball which forms the projecting surface 56 having a shape complementary to that of the housings. To place the measuring head 20 in a defined angular position, the optical guide is rotated to place the ball in one of the housings. Advantageously, the ball screw 55 also provides a locking mechanism to secure the measuring head in the chosen angular position. According to an advantageous design, the proximal end 48 of the body is provided with a stop which limits the orientation of the measuring head to only between 0° corresponding to the position illustrated in Figure 7 and 270°. This stop prevents the measuring head from making complete rotations, thus preventing the data transmission cable 28 from twisting. According to a particularly advantageous embodiment illustrated in Figures 4A and 4B, the hollow longitudinal body 40 consists of an optical guide 41 and an overmolding 42 surrounding the optical guide 41. As a result, the optical guide 41 and the overmolding 42 comprise a distal end corresponding to the distal end 49 of the hollow body 40 and a proximal end corresponding to the proximal end 48 of the hollow body 40. The optical guide 41 guides the light from the light source 21 from the proximal end 48 to the distal end 49 to illuminate an analysis surface of the tooth. Simultaneously, the passage 29, extending from the proximal end 48 to the distal end 49 of the hollow body, allows a cable 28 to pass through for the 8 transmission of data taken by the acquisition means to a data processing unit. The overmolding 42 includes a set of patterns distributed along its outer surface and configured to ensure on the one hand the attachment of the tip 26 to the end 49B of the distal end 49 of the overmolding 42 and on the other hand the mounting of the proximal end 48 in the housing 11 by means of the orientation assembly 50. The patterns form a clip-on pattern 43 at the distal end of the overmolding 42. The tip 26 includes a complementary clip-on pattern 26A. The two patterns 43 and 26A work together to secure the removable tip 26 to the optical guide. The removable tip 26, which is sterilizable and for limited use, can thus be easily mounted or removed from the body 40 manually. Advantageously, the patterns form a first raised thickness forming a first annular shoulder 44 and a second raised thickness 45 forming a second annular shoulder 45. The first raised thickness 44 forms a stop against which an end 14 of the housing 11 rests. The second raised thickness 45 forms an axial positioning stop for the body 40 when the proximal end 48 is mounted in the cavity 53 formed by the two half-shells 51, 52. Advantageously, the patterns also form a plurality of housings 57.1-57.7 made on the outer surface of the overmolding 42, at the proximal end 48 of the overmolding 42. These housings are intended to cooperate with the surface projecting radially on the inner surface of the cavity 53 to ensure the different angular positions of the measuring head 20 relative to the housing 11. Thus, when the measuring head is mounted in the housing 11 as illustrated in Figure 3, one end of the housing 14 rests against the annular shoulder 44 of the overmolding 42. In addition, the proximal end 48 is held in position in the cavity 53 formed by the two half-shells which are fixed in a housing of the housing 11. Preferably, the optical guide and the overmolding 42 are made of a material with lower refractive index than the optical guide material in order to avoid degrading the light guiding conditions. For example, the optical guide is made of polymethyl methacrylate (PMMA) and the overmolding is made of polytetrafluoroethylene (PTFE). Preferably, the optical guide 41 and the overmolding 42 are isolated from the outside by a metallic coating in order to ensure good guidance of the illumination light and isolation of the guide from the outside light. The faces of the guide can be machined to generate patterns designed to optimize the illumination at the output of the guide. As is known, image acquisition means include a sensor 24 and an optical system 22. Sensor 24, for example, is a sensor equipped with a pixel array to provide a signal that allows for the reconstruction of an image of the tooth or a portion of the tooth. The sensor is preferably a field-effect sensor. The sensor is connected to a data processing unit. The light source 21 is fixed on a mounting support 27. The mounting support Tl is able to be positioned on an assembly surface 47 formed on the end 48B of the proximal end 48 of the overmolding 42. Preferably, the Tl support also includes a data processing unit and a light source control board. This board can also be located on a separate electronic board associated with the display electronics. Preferably, the light source includes at least one white LED and LEDs with wavelengths ranging from 448 to 630 nm, fixed to the mounting bracket 27. According to an advantageous embodiment of the invention, the LEDs, the control board, and the optical system are integral with the overmolding 42. Thanks to this specific configuration, the sensor always sees the same distribution for a given LED. Thus, regardless of the orientation of the body or the optical guide 41, the illumination beam on the analysis surface of the tooth is always the same. The use of an optical guide to direct the light from the LEDs to an analysis surface allows for the relocation of the light sources while providing the most homogeneous illumination possible on the analysis surface, regardless of the LED used and the orientation of the measurement head relative to the housing. The optical system 22 includes a lens 25 and polarizing filters 23. The assembly is achieved by fixing the sensor 24 onto a support piece 24.1 which receives a locking latch 30. The lens 25 is screwed onto the support piece 24.1 by means of a very fine thread to adjust the focal length very precisely. The support piece 24.1 with its sensor and carrying the lens 25 is introduced into the optical guide 29 and secured by any means, in particular by gluing. According to an advantageous form illustrated in Figure 5, the optical system 22 includes polarizing filters 23 positioned near the distal end 26A of the tip 26. These filters allow the light reflected by the analysis surface to be eliminated. According to one embodiment of the invention, a first glass plate and a second glass plate sandwich a first polarizing filter 23 for the emitting part and a second filter 23 for the receiving part. The two plates and the two rectilinear polarizing filters, arranged so that their polarization axes are orthogonal, form a disk 23 having a diameter of 16 mm. According to one embodiment, this disc 23 is attached by gluing onto a glass plate which is clipped onto the end of the guide, or according to a variant, the disc 23 is glued directly onto the end 49B of the distal end 49 of the overmolding 42, as illustrated in Figure 5A. Figure 5B shows in more detail the tip 26, which has a roughly tubular shape. This tip is made of an opaque material. It is designed to be attached to the end 49B of the distal end 49 of the overmolding 42. This tip 26 comprises a distal end 26A intended to contact the tooth and a proximal end 26B positioned near the image acquisition means. Advantageously, the distal end 26A is separated from the proximal end 26B by a predefined distance corresponding to a working distance for image acquisition. Another advantage is that the use of this tip eliminates stray light in the vicinity of the analyzed tooth. Furthermore, the tip allows for precise positioning of the measuring head. The proximal end 26B of the tip 26 has a clip pattern 26C on its inner surface which cooperates with a clip pattern 43 formed at the distal end 49 of the overmolding 42 to secure the tip to the body. The tip, which is for single use, can thus be very easily mounted or removed from the hollow body manually. Preferably, the nozzle is in the form of a disposable cap whose tubular shape extends the angled distal end 49 of the overmolding. As a result, the nozzle has an angle of inclination α with respect to the longitudinal axis 46 of the body 40 when it is fixed to the latter, see figure 6. 5. According to another important feature, this tip includes a surface of chromatic reference which allows the measuring device to perform automatic self-calibration.

Claims

12 DEMANDS 1. A dental shade measuring device (1) comprising a housing (11), a handle (10) and a measuring head (20), characterized in that said measuring head (20) comprises: - a hollow body (40) extending along a longitudinal axis (46), said hollow body comprising a proximal end (48), a distal end bent (49) with respect to the longitudinal axis (46), said distal end (49) being provided with a removable tip (26) intended to come into contact with an analysis surface of a tooth; - at least one light source and image acquisition means, attached to the hollow body (40), said hollow body being capable of transmitting light from said light source from the proximal end to the distal end; and in that said apparatus includes an orientation assembly allowing the proximal end (48) of the hollow body (40) to be mounted in the housing (11) so that the measuring head (20) occupies different angular positions relative to the housing (11).

2. Apparatus according to claim 1, characterized in that the orientation assembly (50) comprises at least a first half-shell (51) suitable for being assembled to a second half-shell (52) to form a hollow shell delimiting a cavity (53) configured to receive said proximal end (48), said cavity (53) having on its inner surface a surface (56) projecting radially, intended to cooperate with a plurality of housings (57.1, 57.2, 57.3, 57.4, 57.5, 57.6, 57.7) having a complementary shape, formed on the outer surface of the proximal end (48) to ensure the different angular positions of the measuring head (20) relative to the housing (11).

3. Device according to claim 1 or 2, characterized in that the orientation assembly (50) includes a locking means (55) for locking the measuring head (20) in a defined angular position relative to the housing (11).

4. Apparatus according to any one of claims 1 to 3, characterized in that said hollow body (40) is constituted by an optical guide (41) surrounded by an overmolding (42) comprising a set of fastening motifs (43, 45).

5. Device according to claim 4, characterized in that said pattern set comprises a clip pattern (43) formed on the end (49B) of the distal end (49) of the hollow body (40) to secure the tip (26).

6. Apparatus according to claim 4 or 5, characterized in that said pattern assembly comprises an annular shoulder (45) forming an axial stop for the hollow body (40) when the proximal end (48) is mounted in said orientation assembly (50).

7. Apparatus according to any one of claims 1 to 6, characterized in that said at least one light source (21) is fixed on the end (48B) of the proximal end (48) of the hollow body (40) and said image acquisition means (22, 23, 24) are fixed on the end (49B) of the distal end (49) of the hollow body (40).

8. Apparatus according to claim 7, characterized in that it comprises a cable (28) extending in the hollow body (40) substantially from the proximal end (48) to the distal end (49) to transmit an image from the distal end to the proximal end (48).

9. Apparatus according to any one of claims 1 to 8, characterized in that said image acquisition means comprise a sensor (24) and an optical system (22, 23).

10. Apparatus according to any one of claims 1 to 9, characterized in that said at least one light source (21) comprises at least one white light-emitting diode (LED) and light-emitting diodes (LEDs) whose wavelengths vary between 448 and 630 nm, said LEDs being fixed on a support (27).

11. Device according to claim 10, characterized in that said support (27) comprises a data processing unit and an LED control board.

12. Apparatus according to any one of claims 9 to 11, characterized in that the optical system (22) comprises a lens (25) and at least one polarizing filter (23).

13. Apparatus according to any one of claims 1 to 12, characterized in that the tip (26) comprises a distal end (26A) intended to come into contact with the analysis surface of the tooth and a proximal end (26B), said proximal end being separated from said distal end by a predefined distance corresponding to a working distance for the acquisition of an image.

14. Device according to any one of claims 1 to 13, characterized in that the tip (26) comprises a chromatic reference surface.

15. Device according to any one of claims 1 to 14, characterized in that it comprises a base (17) for placing the device on a flat surface, the base comprising a housing suitable for receiving at least one battery.

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