METHOD FOR MEASURING THE THICKNESS OF DEVICES OBTAINED BY THERMOFORMING

Abstract

The present invention relates to a method for measuring (100) the thickness of devices (20) obtained by thermoforming a sheet of thermoplastic material on a positive mold (10). In particular, the present invention relates to a method for measuring the thickness of orthodontic dental devices obtained by thermoforming processes, such as orthodontic braces for incremental dental repositioning, bites, occlusal guides and so on, which comprises the steps consisting in acquiring (110) a plurality of images of the device (20) obtained by thermoforming in configuration fitted on the positive mold (10) and deriving therefrom a three-dimensional digital model of the assembly consisting of the positive mold (10) and the device (20) obtained by thermoforming fitted on the same (10); acquiring (120) a plurality of images of the positive mold (10) in the absence of the fitted thermoformed device (20) and deriving therefrom a three-dimensional digital model of the positive mold (10) alone; comparing (130) the two three-dimensional digital models derived and calculating thicknesses of the thermoformed device (20) on the basis of the differences detected by the comparison.

Claims

1. Method for measuring the thickness of devices obtained by thermoforming a sheet of thermoplastic material on a positive mold characterized in that it comprises the steps consisting of: acquiring a plurality of images of the device obtained by thermoforming in configuration fitted on the positive mold and deriving therefrom a three-dimensional digital model of the assembly consisting of the positive mold and the device (20) obtained by thermoforming fitted on the same; acquiring a plurality of images of the positive mold in the absence of the fitted thermoformed device and deriving therefrom a three-dimensional digital model of the positive mold alone; and subsequently comparing the two three-dimensional digital models derived and calculating thicknesses of the thermoformed device on the basis of the differences detected by the comparison.

2. Method for measuring the thickness according to claim 1, wherein said acquisition step refers to images only of outer surfaces.

3. Method for measuring the thickness according to claim 1, wherein the comparison step between the two three-dimensional digital models comprises obtaining point by point distances which are present between the two models, said thicknesses of the device coinciding with the distances obtained.

4. Method for measuring the thickness according to claim 1, additionally comprising a step of inserting a plurality of reference targets onto the positive mold, prior to the image acquisition step and the model derivation step.

5. Method for measuring the thickness according to claim 1, additionally comprising a step of aligning the acquired three-dimensional digital models.

6. Method for measuring the thickness according to claim 1, additionally comprising a step of inserting a plurality of reference targets onto positive mold prior to the image acquisition step and the model derivation step, and a step of aligning the acquired three-dimensional digital models, wherein the alignment step comprises superimposing the reference targets present in both three-dimensional digital models.

7. Method for measuring the thickness according to claim 1, wherein the images of the device obtained by thermoforming in configuration fitted on the positive mold and/or the images of the positive mold are acquired by means of an optical scanner.

8. Method for measuring the thickness according to claim 1, wherein the images of the device obtained by thermoforming in configuration fitted on the positive mold and/or the images of the positive mold are acquired by means of a laser scanner.

9. Method for measuring the thickness according to claim 1, wherein the device obtained by thermoforming is an orthodontic dental device and the positive mold is a model of a dental arch.

10. Method for measuring the thickness according to claim 9, wherein the orthodontic dental device is a transparent orthodontic mask.

Description

[0037] In such drawings,

[0038] FIG. 1 is a block diagram of a preferred embodiment of the method for measuring the thickness of thermoformed devices according to the present invention;

[0039] FIGS. 2a and 2b are axonometric views, respectively, of an assembly consisting of a mold and a corresponding device obtained by a thermoforming process on said mold fitted thereon and of the mold alone.

[0040] In the following description, identical reference numerals or symbols are used for the illustration of the figures to indicate construction elements having the same function. Moreover, for clarity of illustration, some references may be not repeated in all the figures.

[0041] The method for measuring the thickness of thermoformed devices will be described below in illustrative and non-limiting terms, with particular reference to the measurement of the thickness of a transparent orthodontic mask. However, the same thickness measurement method is applicable for measuring the thickness of any object obtained by thermoforming.

[0042] With reference to FIG. 1, a preferred embodiment of the method for measuring the thickness of a device obtained by thermoforming according to the present invention, indicated as a whole by 100, is shown.

[0043] The measuring method 100 comprises a first step 110 in which a plurality of images of the positive mold 10 used in the thermoforming of the device with the thermoformed device 20 itself fitted thereon, which in the case in FIG. 2a is an orthodontic mask, is acquired, and a corresponding three-dimensional digital model is derived.

[0044] During the following step 120, the three-dimensional digital model of the positive mold 10 (illustrated in FIG. 2b) is derived in the absence of the mask 20, also in this case through the acquisition of a plurality of corresponding images.

[0045] It should be noted that steps 110 and 120 can be inverted with equivalent result.

[0046] There are three acquisition options; according to the first option, the mold 10 is acquired then thermoformed and finally the mask 20 fitted onto the mold 10 is acquired; according to the second option, the mask 20 fitted onto the mold 10 is thermoformed and then acquired, then the mask 20 is removed from the mold 10 and finally the mold 10 is acquired; according to the third (preferred) option, the mask 20 is thermoformed and then is removed from the mold 10, then the mold 10 is acquired, then the mask 20 is fitted onto the mold 10 and finally the mask 20 fitted onto the mold 10 is acquired.

[0047] In steps 110 and 120, only outer surfaces are acquired, i.e. not surfaces of inner parts of the mold 10 and of the device 20; it is specified that “inner” and “outer” does not refer to the position with respect to a hypothetical “oral cavity”, but refers to the position with respect to the perimeter of the body considered.

[0048] In steps 110 and 120, only upper surfaces are acquired, because the positive mold is positioned with the teeth facing upwards.

[0049] The derivation of three-dimensional digital models can also be made a long time after the acquisition of the images, for example just before the comparison of the models themselves.

[0050] The following step 130 provides that the thickness (for example “whole field”, that is, on a whole surface) is obtained by calculating point by point the distances between the two three-dimensional digital models. Specifically, the coordinates in the space of the corresponding points that make up the surfaces in the two models are compared. For each point of the surface defined by the digital model of the positive mold 10, the point closest to it belonging to the surface defined by the model of the assembly consisting of the mold 10 and the device 20 fitted on the same 10 is located. In this way, the distance between the two points in the space and therefore the thickness of the object fitted is obtained.

[0051] The step of calculating 130 the thickness through the evaluation of the distances between the corresponding points in the two three-dimensional digital models respectively relative to the mold 10, with and without the mask 20 fitted, requires that these models are perfectly aligned.

[0052] It should be noted that for each point of the three-dimensional model of the mold 10 (appropriately selected), we can consider, for example, a point of the three-dimensional model of the mask 20 having minimum distance or a point of the three-dimensional model of the mask 20 located on the perpendicular with respect to the surface of the mold 10. Naturally, a similar consideration can be made (alternatively or in addition) for each point of the three-dimensional model of the mask 20 (appropriately selected).

[0053] It is therefore preferably provided a step 105 for inserting reference targets onto the positive mold 10 before the image acquisition steps and consequent derivation of the three-dimensional digital models 110 and 120.

[0054] Subsequently to the acquisition and derivation steps 110 and 120, but before the step of calculation of the distances 130, an alignment step 125 of the three-dimensional digital models obtained takes place, performed by superimposing the reference targets present in both models derived from the acquired images.

[0055] The insertion step 105 of the reference targets and the alignment step 125 are superfluous if the two images are acquired by the same instrument without the positive mold 10 being displaced between the first 110 and the second 120 acquisition steps. In this hypothesis, in fact, the models derived from the images are already perfectly aligned.

[0056] The features of the method for measuring the thickness of devices obtained by thermoforming object of the present invention as well as the relevant advantages are clear from the above description.

[0057] Additional variants of the embodiments described above are possible without departing from the teaching of the invention.

[0058] Finally, it is clear that several changes and variations may be made to the method for measuring the thickness of devices obtained by thermoforming thus conceived, all falling within the invention; moreover, all details can be replaced with technically equivalent elements. In the practice, the materials used as well as the sizes, can be whatever, according to the technical requirements.