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EP-4510971-B1 - APPARATUS AND METHOD FOR ACQUIRING A DENTAL IMPRESSION BY MEANS OF INTRAORAL DIGITAL SCANNING

EP4510971B1EP 4510971 B1EP4510971 B1EP 4510971B1EP-4510971-B1

Inventors

  • CROVATO, Diego
  • ABRAMI, GABRIELE
  • GUIRAO CANO, Sergio

Dates

Publication Date
20260506
Application Date
20220310

Claims (12)

  1. An apparatus for acquiring a dental impression by means of intraoral digital scanning, where said apparatus is configured to produce a set of data representing a three-dimensional image of at least one portion of the dental arch, said apparatus comprising: - a control unit; - an intraoral scanner connected to the control unit; and - a reference device (1) to be fixed to the dental arch; wherein said reference device (1) comprises: - a support element (10); - three-dimensional reference elements (20) fixed to the support element (10); and wherein said control unit is configured to receive the set of data acquired by the scanner representing a three-dimensional image of at least one portion of the dental arch and of the reference device applied thereto, and to process the acquired data set as a function of a set of predetermined geometric reference data for the reference device (1) provided as input data for the control unit, characterized in that said support element (10) comprises: - a first outer portion (11), to be positioned outside the dental arch, i.e. in the vestibular area; and - a second inner portion (12), to be positioned inside the dental arch, i.e. in the buccal cavity, said first (11) and second (12) portions having a substantially arched shape, the support element (10) further comprises curved extensions (13), formed at a first end of each pair formed by the inner portion (11) and outer portion (12) and, acting as connecting elements which makes said inner portion (11) and outer portion (12) joined together forming a single element with a closed curved profile, wherein a space (14) formed between the inner portion (11) and the outer portion (12) allows the reference device (1) to surround the entire dental arch, when in use.
  2. Apparatus according to claim 1, wherein said reference elements (20) have an axial symmetrical shape with a reference axis.
  3. Apparatus according to claim 2, wherein said reference elements (20) comprise cylinders, cones, truncated cones, spheres or spherical caps.
  4. Apparatus according to any one of the preceding claims, wherein said reference elements (20) have different heights.
  5. Apparatus according to any one of the preceding claims, wherein said support element (10) comprises a curved bar with a cross-section having an area of between 5 mm 2 and 40 mm 2 .
  6. Apparatus according to any one of the preceding claims, wherein the reference device (1) comprises a fixing element adapted to enable fixing of the reference device to the scanabutments (P) of a dental implant.
  7. Apparatus according to claim 6, wherein said fixing element (30) comprising a plate (31) which can be movably coupled to the support element (10), said plate (31) being made of a rigid polymeric material.
  8. Apparatus according to any one of the claims from 1 to 5, wherein the reference device (1) comprises fixing means (40) adapted to enable fixing of the reference device (1) to the scanabutments (P) of a dental implant, said fixing means (40) comprising at least one articulated arms (41) having a first end connected to the support element (10) and a second end, distal, which can be fixed to a pin (P) of the dental implant.
  9. Apparatus according to claim 5, wherein the support element (10) is shaped to have seats or holes at the teeth and scanabutments present on the dental arch.
  10. Apparatus according to any one of the preceding claims, wherein on said reference elements (20), on the support element (10) or on both there are graphic signs allowing better identification of their geometric parameters.
  11. A method for acquiring a dental impression of a subject by means of intraoral digital scanning, said method comprising at least the following steps: - providing a reference device (1) according to any one of the preceding claims; - fixing said reference device (1) to the patient's dental arch; - performing a scan of at least one portion of the dental arch by means of an intraoral scanner to produce a set of data representing a three-dimensional image of the at least one portion of the dental arch and of the reference device (1); - calculating, based on the set of data acquired with the intraoral scanner and on a set of geometric reference data for the reference device (1), a set of corrected data representative of the three-dimensional image of the at least one portion of the dental arch.
  12. Method according to claim 11, wherein the set of data acquired with the intraoral scanner comprises a plurality of points (P) associated with coordinates (r, θ, z) with respect to the origin of a reference system (X, Y, Z) integral with the reference device (1) and wherein the position of each point (P) of the set of acquired data is corrected as a function of a parameter calculated based on the difference between the position of at least one identification point of each reference element in the set of geometric reference data and the position of said identification point in the set of acquired data.

Description

The present invention relates to an apparatus and the relative method for acquiring a dental impression of a subject (generally a patient) by means of intraoral digital scanning. More in detail, the invention relates to an apparatus which includes a reference model, with a known and predetermined geometry, to be used during the scan and a computer system, programmed to process the data acquired during the scan on the basis of the geometric data of the reference model. Restorations in the form of dental prostheses may be needed to address partially or fully edentulous conditions. Traditionally, such restorations are performed by obtaining an impression of the affected areas of the patient's mouth, developing a plaster model from the impression and manufacturing a customized prosthetic device on the plaster model. The impression is used to detect the three-dimensional positions, in space, i.e. in the patient's oral cavity, of the arches, teeth and implants. Taking the impression is the most important and critical step to create a "master" model, usually in dental plaster, i.e. the precise replica of the patient's dental arch, including the dental surfaces and the residual ridges. This model is then used for the construction of the prosthesis. Since the osseointegrated type implant has a high rigidity, its construction must be extremely precise since any inaccuracies, in the jargon "misfits", may cause biomechanical complications with consequent biological effects, that is, in some cases, the reduction of the duration of the implant-prosthesis system, i.e. An early osseointegration thereof. In addition to this, such geometric and dimensional inaccuracies often generate painful conditions for the patient. The traditional technique of taking impressions involves the use of elastic materials, such as salts of alginic acid or silicone materials. While allowing the creation of accurate models, this procedure, in addition to being quite invasive and annoying, creates discomfort for the patient and is laborious and time-consuming. To overcome these drawbacks, intraoral scanning (IOS) has recently emerged as a preferred dental impression technique for conventional and implant dentistry. The intraoral scanning technique typically involves using a handheld scanner provided with optical sensors to acquire a three-dimensional set of data of the area of interest. The resulting set of data may be used to build a model for preparing patient-specific prostheses. An example of using such sets of data to build a model is described in U.S. 2011/183289 A1. The use of these digital technologies has allowed a reduction in the measurement times, waiting for the patient and the creation of the final prosthesis, as well as eliminating the cost of the material for the impression. The expected final goal is to be able to work exclusively on digital (virtual) models, for the final realization of prosthetic crowns or prosthetic implants for the patient, and to be able to manufacture such prostheses with such accuracy as not to require further modification of the prosthesis on the patient, thus limiting the variability introduced by the operator and the consequent human errors. The manufacturing steps include the digitization of both the implant position and the opposite "antagonist" arch, the CAD drawing of the prosthesis and its manufacture. Today, however, these systems still have limits of precision and accuracy to obtain a sufficiently precise digital impression and model. Some known apparatuses also include methods for optimizing the data obtained by the intraoral scanner, such as those described in U.S. 9198627 B2 and WO 2020197116 A1. Even with such apparatuses, although the accuracy has proved sufficiently precise and efficient for the restorations of single teeth or short edentulous segments of teeth, it is instead often contraindicated for the scanning of larger edentulous segments or even in the presence of total edentulism. The intraoral scanner, in fact, is provided with an optical window of limited size; therefore, in order to scan the entire arch it is therefore necessary to process several images acquired in sequence with a software programmed to "join" said images acquired not simultaneously. However, the three-dimensional images provided by the intraoral scanner show some geometric distortions between what was reconstructed and the real positions and shapes of the dental arches. Furthermore, these errors are not uniform, but vary according to the dental section processed. This therefore often involves discrepancies in the digital impression obtained with respect to the real shape, due to which adaptations, sometimes complex, of the prosthesis obtained from the digital impression or in any case of the implant on the patient are required. Relevant prior arts are also exemplified by US 2020/146790 A1, WO 2015/154125 A1, WO 01/34057 A1, WO 2020/182701 A1, and WO 2006/111964 A2. In this context, it is an object of the present